Mr Lieberman had previously told his Irish counterpart Michael Martin that there was no evidence Mossad carried out the murder of a Hamas militant in Dubai.
Spain’s Foreign Minister Miguel Angel Moratinos, whose country currently holds the presidency of the EU, said they were very worried about the forged passports.
He said: "We're extremely concerned that a passport, which is a very rigorous and legal document, can be used in a different manner and for a different purpose."
Shadow Foreign Secretary William Hague attacked Foreign Office Minister Chris Bryant in the Commons over a Mossad source who allegedly told newspapers that MI6 knew that British passports would be used in the killings.
But Mr Bryant said that Dubai police had told British officials three days prior to their announcement that British passports might have been used, and confirmed it just hours before they announced it to the press.
