The Department of Foreign Affairs has revealed that two out of the three fake Irish passports used by a Mossad hit squad contained real passport numbers.

Among the eleven people who are suspects in the assassination of a senior Hamas figure in Dubai, six carried British passports, three held Irish passports and the rest traveled on German and French passports.

Although the passport numbers were identical in two cases, the identities were not.

The Department of Affairs had previously denied that the passports numbers used by the assassins were real.

However, the Irish Ambassador to Abu Dhabi, Ciaran Madden, said that officials had told him the passport numbers were real.

The Minister for Foreign Affairs Michael Martin said that he treated "any activity which would jeopardize the integrity of the Irish passport" extremely seriously.

"Our passport is widely regarded and respected throughout the world as being of the highest quality. We have invested very heavily in extra security features so that our citizens can travel in safety.

“Actions which endanger our well-earned reputation in this area have the potential to affect the security of all our citizens travelling overseas. I am determined to maintain the good name of Irish passports,” said Martin.

While British Prime Minister Gordon Brown has started a full investigation into the matter, Ireland is in close contact with the United Arab Emirates and Irish Police.

Department of Foreign Affairs officials are also contacting officials in London, Paris and Berlin in relation to the incident.

The Irish Times newspaper has revealed that the Israeli ambassador to Ireland, Zion Evrony, will be summoned to the Department of Foreign Affairs. The Israeli ambassador to England will also have to face Gordon Brown and discuss alleged links between some of the legitimate passport holders and Israel.

Israeli Foreign Minister Avigdor Lieberman dismissed claims that Israel was behind the assassination of the Hamas operative.

"There is no reason to think that it was the Israeli Mossad, and not some other intelligence service or country up to some mischief,” said Lieberman.

Israel has been quick to dismiss claims of Mossad’s involvement in the Hamas assassination. A former Mossad official Rafi Eitan said, “Mossad was not behind the assassination of Mahmoud al-Mabhouh, but rather a foreign organization that is trying to frame Israel.

Hamas militant armed wing Izz-elDeen al-Qassamsaid said it "will never rest until they reach his killers."