LONDON: British diplomats meet Israel's ambassador Thursday to discuss fake British passports used by alleged killers of a Hamas chief amid speculation its Mossad spy agency was behind the murder in Dubai.

The Israeli envoy to London was summoned to the Foreign Office Wednesday , said a government spokesman, hours after Prime Minister Gordon Brown pledged a "full investigation" of the passports affair.

In another sign of growing diplomatic tensions over the murder, Ireland also voiced concern over the use of fake Irish passports.

Speculation about who was behind the killing of Mahmud al-Mabhuh last month has centred on Israel's Mossad intelligence services, which have used agents with fake foreign passports for such operations in the past.

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Dubai's police chief this week released the photos and names of the 11 European passport holders -- six from Britain, three from Ireland, one from Germany and one from France -- alleged to have been members of the hit squad.

All the countries except Germany have since said their passports had been faked.

Britain had abstained from talking about a possible Israeli link but on Wednesday it announced it wanted to clarify matters with Israel.

"The defrauding of British passports is a very serious issue. The government will continue to take all the action that is necessary to protect British nationals from identity fraud," the British government spokesman said.

"Given the links to Israel of a number of the British nationals affected, there will be a meeting between the FCO Permanent Under Secretary and the Israeli ambassador (on Thursday)," the spokesman said.

Lawmaker Menzies Campbell, a member of the British parliament's foreign affairs committee, urged Israel to drop its traditional refusal to talk about security matters in the face of "an abuse of British sovereignty."

"To take refuge in the traditional Israeli view that we don't comment on intelligence and security matters... in my view does not stack up," he told BBC television, and urged the envoy to say whether or not Mossad was involved.

Israeli Foreign Minister Avigdor Lieberman sought earlier Wednesday to play down the escalating row, saying there was no reason to believe the Jewish state's spy agency was involved.

"There is no reason to think that it was the Israeli Mossad and not some other intelligence service or country up to some mischief," he told local media.

Before London summoned the envoy on Wednesday, Britain's prime minister vowed "to carry out a full investigation into" the passport affair amid growing calls from lawmakers on all sides for the government to take a stand.

"The British passport is an important document that has got to be held with care," Brown told London's LBC Radio. "The evidence has got to be assembled about what has actually happened and how it happened and why it happened."

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The probe will be led by the Serious Organised Crime Agency, "in close co-operation with the Emirati authorities," the government spokesman said.

Meanwhile Ireland -- which had initially said the details of the three Irish passport holders were entirely false -- said Wednesday it had received new information from authorities in the United Arab Emirates.

The new data "confirms that the passports used were fraudulent," said Foreign Minister Micheal Martin, but added: "The new information ... indicates that genuine Irish passport numbers were used.

"These numbers correspond to actual numbers on three legitimate Irish passports," although the identities on the forged passports "do not correspond to those recorded on the valid passports carrying the same numbers."

Irish authorities were therefore "urgently endeavouring to contact the three Irish citizens who hold or have held passports containing these numbers," he said, while requesting privacy for those individuals.

Martin added: "The Minister for Foreign Affairs regards any activity which would jeopardise the integrity of the Irish passport as extremely serious.

"Our passport is widely regarded and respected throughout the world as being of the highest quality."