Senior Conservatives have assured opposition leader Tzipi Livni that a Tory government would change the law that allows magistrates to issue arrest warrants for foreign politicians accused of war crimes.

Shadow business secretary Ken Clarke and shadow attorney general Edward Garnier met her in Israel as part of a party charm offensive.

Mr Garnier said: "The Tories will change the law if this government doesn't, although we remain happy to co-operate if there is still an appetite for reform. There is support this from David Cameron and William Hague downwards. Our courts will not be used as the venue for street protest."

The government has set itself a new March deadline to push through the legislation. But senior sources in the Jewish community and the Foreign Office have told the JC they believe the chances of it reaching the statute book before the election are slim.

Foreign Secretary David Miliband promised a change in December after an arrest warrant was issued for Ms Livni. She has since said she will travel to Britain and face arrest if the government does not resolve the issue.

The change could still be added at the report stage of the Crime and Security Bill, which has a deadline of March 1 for tabling amendments.

Justice Secretary Jack Straw has invited the Board of Deputies and the Jewish Leadership Council to discuss the issue on February 23. He will meet Labour Friends of Israel the same day.

It is understood the organisations will demand a definitive answer from Mr Straw before going public about their dismay at the mixed messages coming from government.

Mr Straw denied he was blocking the law change under pressure from Muslim groups.

His spokesman said: "For the record, this is completely untrue. Jack has not spoken to the Muslim Council of Britain about this issue, or to any of the Muslim leaders in his constituency or elsewhere."

MCB will have ample opportunity to lobby the Justice Secretary before his meeting with the Board and the JLC, however, as Mr Straw is the guest of honour at the organisation's fundraising dinner on February 22.