The shadow foreign secretary, William Hague, says the Israeli government has "more questions" to answer about the apparent use of false British passports by a team of assassins who killed a leading Hamas commander in Dubai.
Mr Hague said that he wanted the Foreign Office to confirm reports that the Dubai authorities had contacted the British Government at the end of January to ask for assistance in this case.
"I would like to know when the government, when the Prime Minister, when the Foreign Secretary were informed about it and what action they decided to take then," he told Today presenter, John Humphrys.
"Because it may be that they have already had discussions with the government of Israel. It may be that they have already sought assurances from the government of Israel. It was only yesterday when this became a matter of media attention that the Prime Minister ordered a full investigation."
The Israeli ambassador in London has been asked to appear at the Foreign Office later this morning to explain his government's involvement in the death of Mahmoud al-Mabhouh on 20 January.
It has been widely claimed that agents of the Israeli secret service, Mossad, assassinated the Hamas leader in a hotel last month. Some of them are believed to have been travelling on forged documents, using the stolen identities of six Britons who live in Israel.
Speaking on today's programme Mr Hague said that there was "great concern" about the forging or cloning of passports and that "our own particular national interest is in protecting the passports of UK individuals".