The publication of a damning report into how the authorities handled child exploitation in Rotherham has prompted the leader of the local council to resign.

The independent inquiry by Professor Alexis Jay found that 1,400 youngsters suffered sexual exploitation including rape and trafficking in the South Yorkshire town over a 16-year period.

We know that the case which led to the conviction of five men in Rotherham is not the only one of its kind. Could the abuse that has already come to light be just the tip of the iceberg?

Here’s what we know (and what we don’t) about the child grooming gangs.

How many gangs?

The Child Exploitation and Online Protection Centre (Ceop) – the national anti-paedophile police command – divides networks of sex offenders into two groups.

So-called ”Type 1 offenders” target young people “on the basis of their vulnerability, rather than as a result of a specific preferential sexual interest in children”.

Ceop received intelligence from 31 out of 43 police forces on groups like this who were known or suspected to have abused vulnerable children in 2012.

FactCheck: what do we know about the grooming gangs?

There were 57 such groups, ranging from two to 25 suspects, on the radar of those 31 constabularies. We don’t know if any have now been convicted.

So-called “Type 2″ groups – where the offenders have a long-standing sexual interest in children, were much less common. Only seven known or suspected paedophile rings were reported to Ceop.

It is possible to track cases that have been through the courts via media reports, although this is pretty unscientific.

In 2011 the Times journalist Andrew Norfolk identified 17 cases that had led to convictions where there had been a similar pattern of grooming.

In all cases, the victims were vulnerable teenage girls, often in the care of social services. They were approached on the street by men, befriended and plied with alcohol or drugs, before being sexually abused.

Updating the list to include more recent convictions that fit the same pattern, we find that there have been at least 27 similar cases in the last decade.

By date of conviction, we have evidence of such exploitation taking place in Keighley (2005 and 2013), Blackpool (2006), Oldham (2007 and 2008), Blackburn (2007, 2008 and 2009), Sheffield (2008), Manchester (2008 and 2013) Skipton (2009), Rochdale (two cases in 2010, one in 2012 and another in 2013), Nelson (2010), Preston (2010) Rotherham (2010) Derby (2010), Telford (2012), Bradford (2012), Ipswich (2013), Birmingham (2013), Oxford (2013), Barking (2013) and Peterborough (2013).

This is based on a trawl of news sources so is almost certainly incomplete.

Race and religion

The Jay report into failings in Rotherham says: “By far the majority of perpetrators were described as Asian by victims, yet throughout the entire period, councillors did not engage directly with the Pakistani-heritage community to discuss how best they could jointly address the issue.

“Some councillors seemed to think it was a one-off problem, which they hoped would go away. Several staff described their nervousness about identifying the ethnic origins of perpetrators for fear of being thought racist; others remembered clear direction from their managers not to do so.”

Ceop data about the ethnicity of offenders and suspects identified by those 31 police forces in 2012 is incomplete.

The unit says: “All ethnicities were represented in the sample. However, a disproportionate number of offenders were reported as Asian.”

Of 52 groups where ethnicity data was provided, 26 (50 per cent) comprised all Asian offenders, 11 (21 per cent) were all white, 9 (17 per cent) groups had offenders from multiple ethnicities, 4 (8 per cent) were all black offenders and there were 2 (4 per cent) exclusively Arab groups.

Of the 306 offenders whose ethnicity was noted, 75 per cent were categorised as Asian, 17 per cent white, and the remaining 8 per cent black (5 per cent) or Arab (3 per cent).

By contrast, the seven “Type 2 groups” – paedophile rings rather than grooming gangs – “were reported as exclusively of white ethnicity”.

Ceop identified 144 victims of the Type 1 groups. Again, the data was incomplete. Gender was mentioned in 118 cases. All were female. Some 97 per cent of victims were white.

Girls aged between 14 and 15 accounted for 57 per cent of victims. Out of 144 girls, 100 had “at least one identifiable vulnerability” like alcohol or drug problems, mental health issues or a history of going missing. More than half of the victims were in local authority care.

The 27 court cases that we found led to the convictions of 92 men. Some 79 (87 per cent) were reported as being of South Asian Muslim origin.

Three were white Britons, two were Indian, three were Iraqi Kurds, four were eastern European Roma and one was a Congolese refugee, according to reports of the trials.

Considerable caution is needed when looking at these numbers, as our sample is very unscientific. There are grooming cases we will have missed, and there will undoubtedly be offences that have not resulted in convictions.

Why are so many victims white?

We’re into the realm of opinion now.

Sentencing nine men in 2012 over offences in Rochdale, judge Gerald Clifton told the defendants they had treated their victims “as though they were worthless and beyond all respect”, adding: “I believe that one of the factors that led to that was that they were not of your community or religion.”

But at the Derby trial in 2010 the judge said he thought the race of the victims and their abusers was “coincidental”.

One of the victims of the Oxford gang told the Guardian that her abusers had asked her to recruit other teenagers and “specified that they wanted only white girls”.

Ceop says: “The comparative levels of freedom that white British children enjoy in comparison to some other ethnicities may make them more vulnerable to exploitation.

“They may also be more likely to report abuse. This is an area requiring better data and further research.”

How many children are at risk?

A report by the Office of the Children’s Commissioner found that 2,409 children were confirmed as victims of sexual exploitation in gangs and groups in the 14 months between August 2010 to October 2011.

If that sounds low compared to the 1,400 identified in Rotherham alone, remember that this number covers 16 years.

This probably only scratches the surface of the real number of victims, and the children’s commissioner said that at least 16,500 children had been identified as being “at risk of sexual exploitation” during one year.

How kids are being groomed

1. Targeting. A vulnerable girl is identified by a gang leader – she could be part of a loving family or in care. They are sometimes as young as 11. Usually chosen for their looks but sometimes because they are getting into trouble at school or at home.

2. Recruitment. Young boys are used by the gangs to recruit the girls, and they are often related to the gang members. They introduce the girl to one member of the gang.

3. Grooming. Girls are told they are “beautiful”, “gorgeous” and so on. They are showered with gifts such as clothes, perfume and cosmetics. Mobile phones are given – then used by the gang to control the girls and track them.

4. Isolation from family, or from social workers if in care. Girls are told to keep their relationship with the older man secret. They are taken to adult clubs and bars.

5. Introduction to drinking, smoking and taking drugs. Encouraged to start with cannabis and move on to harder drugs. Often the girls get hooked and gangs use their addiction to control them.

6. Rape by the initial gang member, who girls are made to feel is their boyfriend. But then he starts to pass the girl around. Before long she is being pimped out regularly and made to sleep with sometimes dozens of men. By now they are completely under the control of the gang.

7. Control. Parents often find themselves powerless to stop what is going on – and sometimes have no idea that it is going on.

8. Dumping. Once the gang leader is “bored” with the girl she can be trafficked hundreds of miles away from home to become a prostitute – and become “just another teenage runaway”.

The secret networks of Paedophile gangs

A secret network of organised child sex traffickers and paedophile rings are being operated within British cities by gangs ~ These men have been involved in the grooming and organised rapes of young white girls as young as 11 years old.

Approximately one in six of the sexually exploited children say they have been moved between cities and passed around between paedophiles and asscociated paedo rings. Its a “hidden” problem in which vulnerable youngsters, many of whom have run away from home, are shunted around the country to increase their isolation. “Many children are being abused through prostitution, it became apparent that some young people were being moved around the UK, or from town to town, by abusing adults who will use the children for the purpose of sexual exploitation,”

So why are such vile crimes taking place in so-called modern, civilised Britain by gangs?

One reason is the money that can be made. According to Scotland Yard, a gang can reap £300,000 a year from prostituting a young white girl. There is more money in selling a girl for sex than peddling drugs — especially if she is a virgin and free of sexual diseases.

And then there is a controversial, but relevant, cultural issue. Asian men of Pakistani heritage often believe white girls have low morals compared with Muslim girls. ‘They wear what they call “slags” clothing, showing much of their bodies and “deserve what they get”

The girls are held in contempt by the gang members, who do not even call them by their own names. They refer to each one by the same generic term, either to the girls themselves or to their Asian friends on their mobile phones — the Urdu term ‘gori’, which means simply ‘white-skinned female’.

To add a further twist to this ­brutal cultural divide, the gangs hide their own names from the girls. They call themselves by unidentifiable nicknames, a simple trick which makes the police’s job of tracing the culprits more difficult. And, of course, the girls have no idea who they really are.

In the cases that have come to court in the north of England, whether in Rochdale, Rotherham or in Derby, the modus operandi is invariably the same. A schoolgirl is out with her friends in the town centre, often on a ­Saturday afternoon or after class on her way home. She’s bored, so when a group of smiling men pull up in a flash car blaring rap music she takes notice. The men, smartly dressed, start their chat-up routine. They ask her to ‘chill’ with them. They say ‘come for a ride’ and tell her she’s pretty. They promise they will buy her a meal at any place she chooses.

Once in the car, they produce a plastic cup of vodka and give it to her in the back seat. They hand her a cigarette or a spliff of cannabis, too. The girl is befuddled, but charmed. The gang plays a waiting game, telling her to meet them tomorrow at the same place. She gives them her mobile phone number and they warn her she must not tell her parents about anything that has gone on.

The family and cultural norms of their community means they are expected to marry a first cousin or other relative back in a village of their family or wherever the family comes from. Therefore, until that marriage is arranged they look out for sex.

At the point in their lives when they are ready for this sort of activity, Pakistanis cannot go to asian girls because it would be a terrible breach of the honour of the community and their family to have sex with an Asian girl before marriage. The reason Pakistani men targeted very young white girls was because older white girls knew that a relationship with an Pakistani youth was unlikely to last as the community would seek an arranged marriage with someone from the asian sub- continent.

Police and groups campaigning to protect women insisted that the grooming of youngsters is not segregated along race lines, though there is concern at the attitudes of some young Asian men towards white girls.