Six British-Israelis say they are not the men pictured in the suspects' passports
UK authorities are launching an inquiry into how fraudulent British passports were used by the alleged killers of a Hamas commander in Dubai.
The Serious Organised Crime Agency will look at how passports bearing the names of six British-Israelis were linked to the murder of Mahmoud al-Mabhouh.
Dubai police believe 11 "agents with European passports" killed him.
The Foreign Office has summoned the Israeli ambassador for a meeting on Thursday to discuss the matter.
Israel says there is no evidence that its security service Mossad had any involvement in the killing.
However, several commentators say it bears the hallmarks of a Mossad assassination.
Among them is Labour's Commons Foreign Affairs Committee chairman Mike Gapes who says if it was not carried out by Israel it was by "someone trying to make sure it looks like the Israelis".
ANALYSIS
Katya Adler, BBC Middle East correspondent
Israel is alive with rumour as to whether Israel's intelligence service, Mossad, murdered Hamas operative Mahmoud al-Mabhouh.
Mossad has used fraudulent foreign passports and stolen identities to carry out its missions in the past, provoking diplomatic rows with a number of friendly countries.
Former Israeli secret service officer, Gad Shimron, says agents steal identities to escape tougher security checks. But would Mossad want to point the finger at innocent Israeli citizens?
At least five of the names listed by Dubai match those of Israeli dual nationals.
Maybe Mossad thought this was a clear way, without making a public declaration, of letting the world know it organised the murder - thereby sending a warning to Israel's enemies abroad.
It is possible another country masterminded the attack, designing it to look like a clumsy Mossad operation. Or maybe Israel co-operated with others.
"Israel has... a policy of targeted assassinations," he said, adding its agents had previously used faked passports from friendly countries, despite assuring Britain in 1986 that the practice would stop.
But Israeli Foreign Minister Avigdor Lieberman told Israeli Army Radio: "There is no reason to think that it was the Israeli Mossad and not some other intelligence service or country up to some mischief."
Israel had a "policy of ambiguity" on intelligence matters, he added.
Prime Minister Gordon Brown told London's LBC 97.3 FM radio station: "The evidence has to be assembled about what actually happened, about how it happened and why.
"We have to make sure everything is being done to protect [the British passport]."
On Wednesday night, the Foreign Office pledged "to take all the action that is necessary to protect British nationals from identity fraud".
It said the British embassy in Tel Aviv was ready to support those affected by the Hamas shooting case.
"We need to ensure a full investigation is carried out into the fraudulent use of these passports," the Foreign Office said.
"The Serious Organised Crime Agency (SOCA) will lead this investigation, in close co-operation with the Emirati authorities."
SOCA has confirmed that photographs and signatures on the passports used in Dubai do not match those on passports issued by the UK.
The Conservatives have called on Foreign Secretary David Miliband to spell out what action he had taken to find out how UK passports were used.
In a letter, shadow foreign secretary William Hague asked when the Foreign Office first learned of suspicions about the passports and what contacts Mr Miliband had made with Israeli officials.
Mr Hague said the alleged forgery was "a matter of great concern" and raised the possibility it could happen in cases involving terrorism.
"We need to know if the home secretary and foreign secretary are confident that existing mechanisms are sufficient to prevent further such abuses from happening," he added.
'In shock'
Dr Rosemary Hollis, a Middle East analyst from London's City University, said the development would "raise suspicions" generally that British travellers "might conceivably be up to no good".
The men who share names with the suspects have dual British and Israeli citizenship.
They are Melvyn Adam Mildiner, Paul John Keeley, James Leonard Clarke, Stephen Daniel Hodes, Michael Lawrence Barney and Jonathan Lewis Graham. They all deny involvement in the killing.
The details of the suspects and their passport photos were released by officials in Dubai earlier this week.
Salford-born Mr Hodes, 37, said he had not left Israel for two years and was "in shock".
"I don't know who's behind this. I am just scared, these are major forces," he told Israeli television.
Mr Mildiner, 31, told the Jerusalem Post: "Clearly it isn't me.
"The details are not correct. The date of birth is wrong. I went to bed with pneumonia and woke up a murderer," he said.
The men's family names are not common in Israel, according to the BBC's Middle East correspondent, Katya Adler.
The Irish Republic's government has confirmed that numbers on suspects' passports were legitimate.
But Dublin said they did not match records for the names of Gail Folliard, Evan Dennings and Kevin Daveron, which had been used.
Its Department of Foreign Affairs said officials were urgently trying to contact the three citizens who hold or have held passports with these numbers.
France and Germany have also reportedly raised doubts over the identities of two suspects who used a French and a German passport.
Hamas killing
Police in Dubai have released images of 27 people they believe are behind the killing of a senior Hamas commander. The suspects are accused of using fake passports bearing their own pictures, but the names of innocent citizens.
Twelve of the passports used were British (shown on previous slide). The other 15 on the list are reported to have used stolen identities from Australian, French, Irish and German citizens.
The 27th suspect used the alias Joshua Aaron Krycer - a stolen Australian identity (pictured left). Police say the suspects used their fake documents to travel to Dubai in groups, flying from Zurich, Rome, Paris and Frankfurt.
One of the victims of the identity theft was British-Israeli Paul John Keeley (pictured right). The passport used by one of the suspected assassins bore his name, but featured a photograph of another man (pictured left).
Palestinian militant Mahmoud al-Mabhouh was killed in his hotel room in Dubai on 20 January. Police claim one of the suspects, pictured on the left, went to a hotel to put on a disguise. He is seen leaving a toilet wearing a wig.
Surveillance cameras also recorded Mr Mabhouh, circled in red above, at the hotel's reception before his death. At the bottom of the image the head of one of the suspects can be seen. As Mr Mabhouh leaves, the suspect follows.
Mr Mabhouh is trailed into the lift by a number of the suspects, including two pictured here in tennis gear. Investigators believe he had been followed from Syria to Dubai where it is thought he wanted to buy weapons for Hamas.
When Mr Mabhouh leaves the lift, police say two of the suspects can be seen following him down the corridor. He was later found dead in his room. A post-mortem report said he had been electrocuted and suffocated.
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Mr Mabhouh was murdered in his hotel room in Dubai on 20 January.
Reports have suggested he was there to buy weapons for the Palestinian Islamist movement, Hamas. Hamas has accused Israeli agents of killing him.
Two Palestinian suspects were being questioned about the murder. Police said they had "fled to Jordan" after the killing, without releasing their names.
Officials in Dubai, who have issued arrest warrants, said the team appeared to be a professional hit squad, probably sponsored by a foreign power.
They released CCTV footage which they said showed some of the suspects in disguises, including wigs and false beards, in the hotel near Dubai's international airport.
The suspects allegedly trailed Mr Mabhouh when he arrived in Dubai from Syria.
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CCTV of Hamas murder suspects released by Dubai police
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