The changes won praise from Israel, which had issued vigorous calls for change after former foreign minister Tzipi Livni cancelled a trip to London in 2009 because Palestinian campaigners sought her arrest for war crimes.
A spokesman for the Israeli embassy said: “The cloud that has hung over the UK’s ability to play a role in our area has been lifted, and should no longer cast a shadow over the diplomatic relationship between our two countries.
“We are hopeful that this correction will finally close that loophole which was abused by opportunistic groups promoting their sinister purposes.” Matthew Gould, the British ambassador to Israel, telephoned Mrs Livni to inform her that the Police Reform and Social Responsibility Act, where the change was inserted, had received Royal Assent.
He said the amendment ensured that “the UK’s justice system can no longer be abused for political reasons”.
“The change will ensure that people cannot be detained when there is no realistic chance of prosecution, while ensuring that we continue to honour our international obligations,” he said.
The new law was however likely to draw condemnation from human rights groups. Amnesty International had earlier accused the Government of proposing to hand war criminals “a free ticket to escape the law”.
Until yesterday, private individuals could start prosecutions for human rights abuses by applying to a magistrate for an arrest warrant under “universal jurisdiction law”, which Britain followed as a signatory to major human rights treaties.
It was first used in 1998 by the campaigning Spanish judge, who sought the extradition of Gen Augusto Pinochet for crimes committed as Chile’s dictator.
Various activists later attempted to obtain warrants to arrest visiting dignitaries such as Henry Kissinger, the former US Secretary of State, Bo Xilai, a senior Chinese Communist Party official and Mrs Livni, who is now Israeli opposition leader.
The new law requires the consent of the Director of Public Prosecutions before an arrest warrant can be issued in universal jurisdiction cases, meaning political considerations regarding allies such as Israel are more likely to be taken into account.
Shortly after coming to power, the Government committed to changing the application of the law, but had angered Israel by dragging its feet