By Richard Spencer in Dubai and Aislinn Laing
Police in Dubai now say 12 cloned British passports were used in the killing of Mahmoud al-Mabhouh, as the total number of suspects rose to 26.
One of the Britons whose passport was faked was named as Gabriella Barney, originally from Bury, Lancs, who is thought to have moved to Israel as a child.
She was one of six women who have now named in connection with the assassination of Mr Mabhouh, who was found dead in his hotel room on Jan 20.
The Foreign Office said the photographs and signatures on the newly-released passports did not match those of the Britons whose names and dates of birth were held on file.
The mother of one of the Britons named, Mark Sklar, 30, told The Daily Telegraph her son, who now lives in Israel, had never been to Dubai.
Rachel Sklar, who lives in Staines, Middlesex, said: "He's just a normal guy. I think he'll be quite worried by this."
The other Britons whose passports were used were Roy Cannon, 62, Stephen Drake, 54, Philip Carr, 35, and Daniel Schnur, 32.
Police revealed new details about the murder including fresh CCTV footage of the hit squad in action.
It showed the suspects in various locations across the city, including the airport and hotels, in similar positions to those shown in the original footage. Some were posing as couples as they entered and left hotels.
It also emerged that one of the assassins used a credit card issued by the Nationwide Building Society and two used cards issued by the British firm IDT Finance – where Mr Sklar works.
Another 13 suspects used credit cards issued by the same American bank, Metabank, to book flights and hotel rooms.
The six Britons were among 15 newly-identified suspects, who also carried French, Irish and Australian passports.
One of the Australian men whose passport was cloned, Adam Korman, 34, said from his home in Tel Aviv: "I am shocked, it's identity theft – simply unbelievable.
"I have been frightened and shocked since receiving the news. It's irresponsible and a violation of human and individual rights to do such a thing."
Mr Mabhouh was given an electric shock and then smothered with a pillow while staying at the Al Bustan Rotana Hotel near Dubai Airport. He is thought to have been lured there from his home in Syria on the pretence of buying arms for Hamas.
Police also gave more information about the movements of the assassination squad.
They said the team flew in from four European locations – Zurich, Rome, Paris and Frankfurt – before leaving after the killing, in some cases within minutes.
The suspects scattered across the world in destinations included Hong Kong, Doha, Amsterdam, Paris, Bangkok and Frankfurt, with a number reuniting in Zurich.
In an bizarre twist, it emerged two of the suspects, both using Australian passports, fled by boat to Iran, a sworn enemy of Israel.
It heightened suspicions Mr Mabhouh may have been betrayed by someone he considered an ally. Police have already arrested two Palestinians, said to be members of Hamas's rival Fatah, as suspects and a member of Hamas has been detained in Syria, accused of helping the assassins.
Britain, France, Ireland and Germany have already called in Israeli ambassadors, angered by the use of their nationals' passports in the operation.
A Foreign Office spokesman said: "We believe that passport details were fraudulently used as in the previous cases. We are seeking to contact these other six as we did before to offer consular assistance."