A Mossad agent has apparently claimed that British intelligence was tipped off hours before about a high-profile assassination, and that British passports would be used.

Although the target, Hamas military leader Mahmoud al-Mabhouh, and the location, a luxury hotel in Dubai, were not named, the source told the Daily Mail that MI6 knew the operation was imminent.

The Mossad agent reportedly said that British ministers were “going through the motions” by calling in the Israeli ambassador Ron Prosor yesterday.

The Foreign Office, however, insists that ministers knew nothing about the six British passports, used to cover the identities of the assassins, before the names were released by Dubai police.

A Foreign Office spokesman said: “We received the details of the British passports a few hours before the press conference [by police in Dubai]. We were able to respond to the Dubai authorities on the authenticity of the passports the next day.'

Dubai police chief, Dahi Khalfan Tamim, has said he is almost “99 per cent certain” that the killing of Mr al-Mabhouh was the work of Mossad.

Two Palestinian men are currently in custody in Dubai, believed to be former members of Hamas who had recently defected to Fatah.

Interpol has issued international “wanted” notices for the 11 assassins who were caught on CCTV checking into a room across the hall from Mr al-Mabhouh.

Four of the assassins then broke into his room while he was out, and pounced on his return.