A legal loophole which has allowed hundreds of child abusers to escape prosecution has been closed, Justice Secretary Kenneth Clarke has said.

From Monday anyone who deliberately causes or allows serious physical harm to a child or vulnerable adult faces up to 10 years in prison.

Taking effect in England and Wales, it also enables prosecutions of people who stay silent or blame someone else.

The justice secretary said the move was a boost to child protection.

Police believe as many as 20 cases of child abuse, and three in which the victims were vulnerable adults, went unpunished in 2010 because of the gap in the existing legislation.

“All the people with an interest in protecting vulnerable people will agree that we have closed an obvious gap in the law and from now on if you fail to take steps to stop a child being killed you’re equally responsible,” he said.

The new offence, the Domestic Violence, Crime and Victims (Amendment) Act 2012, is due to come into force on Monday.

Guidance is being sent to prosecutors, judges and others on the new law.

The move follows a number of cases where prosecutions could not be brought because it was impossible to identify the individual responsible for the abuse.

By way of example, the Ministry of Justice cited the cases of a five-month-old baby who suffered a brain haemorrhage and fractured skull, and a two-week-old with a broken collar bone, ribs and leg.

Nobody was charged in either case, however the injuries were not thought to be accidental.

The 2007 death of Baby Peter in north London, after months of abuse, was widely publicised.

The child had suffered more than 50 injuries despite being on the at-riskregister and receiving 60 visits from social workers, police and health professionals over an eight month period.

Two years later his mother, her boyfriend and a lodger were jailed for causing or allowing Peter’s death.

But if a child was abused like Baby Peter and lived, there would have been no way to bring those who had caused the horrific injuries to justice.

“We want to do everything possible to ensure that the most vulnerable members of our society are kept safe in their homes, and those that abuse their power do not evade justice,” said Mr Clarke.

Andrew Flanagan, chief executive of the NSPCC, said the change in the law was “a real victory for children and has the potential to bring many more child abusers to justice”.

“Adults can no longer inflict horrific injuries on children and get away with it by staying silent or blaming each other,” he said.