David Miliband insisted today that he was determined to discover how fake British passports were used in a hit linked to the Israeli secret service Mossad.
As the fallout from the assassination of a Hamas commander continued, the Foreign Secretary branded the abuse of ID documents "outrageous" and demanded that Tel Aviv co-operate fully with the UK's investigation.
But, after being called in to discuss the situation with officials in London this morning, Israel's ambassador, Ron Prosor, flatly denied there was any "additional information" to give.
Dubai police have revealed that cloned passports belonging to six British Israelis and three Irish citizens were among 11 European identity papers used by a hit squad who allegedly killed Mahmoud al-Mabhouh in the Gulf state last month.
Senior officers say they are "99% certain" that Mossad was behind the murder. Tel Aviv has refused to confirm or deny the link.
Tonight, Interpol put out an alert in a bid to trace the 11 members of the alleged hit squad and prevent them travelling using the false passports.
Mr Miliband told reporters he wanted to give Israel "every opportunity to share with us what it knows about this incident".
"We hope and expect that they will co-operate fully with the investigation that has been launched by the Prime Minister and will be undertaken by the Serious Organised Crime Agency (Soca)," he said.
Mr Miliband rejected suggestions that the UK Government was merely "going through the motions" of asking questions about the incident.
"There's obviously been a very serious incident involving British passports... we think it is right to have the investigation the Prime Minister has launched," he said.
"That is not going through the motions, that is the rightful business of government."
He added: "We want to get to the bottom of the issues of the fraudulent use of passports and their potential use. That is the most important thing to do."
The passports used did not contain microchips and the new-style documents would not be as easy to abuse, he added.
Speaking on a visit to the North East today, Gordon Brown said: "We have got to know what happened to British passports - it's as simple as that. It's an investigation that has got to take place before any conclusions are drawn."
After holding a 20-minute meeting with the head of the diplomatic service, Sir Peter Ricketts, this morning, Mr Prosor told journalists: "I was unable to add additional information to Sir Peter Ricketts's request."
Tel Aviv's ambassador to Ireland, Zion Evrony, delivered a similarly blank message after an hour of discussions with diplomat David Cooney in Dublin.
"I told him I don't know anything about the event - beyond that it is not customary to share the content of diplomatic meetings," Dr Evrony said.
It is believed the Hamas commander was in Dubai to buy weapons for the militant Palestinian movement when he was killed in a luxury hotel room on 19 January.
Dubai police chief General Dahi Khalfan said he was 99% sure Israel was involved. He told the Gulf News: "All elements strongly indicate the involvement of the Mossad."
Soca has confirmed photographs and signatures on the passports used in Dubai do not match those on passports issued by the UK.