A British man allegedly pushed a stag do friend off a boat on a Lisbon river while he was “unconscious and without a life jacket”, it emerged today.1boatThe reveller has been made an official suspect after witnesses identified him as the author of the drunken prank. Police divers and a Portuguese air force helicopter were mobilised at dawn this morning for the third day of an ongoing search for the missing 32-year-old, who is also British.

The unidentified man, part of a stag do group of 12 Brits and an Australian, was on board a chartered sailing boat on Lisbon’s River Tagus when the incident occurred just after midday on Saturday. Around 30 rescuers are involved in a sea and air search, which is being conducted during the daytime and suspended at nightfall.

A source close to the case said officers held out little hope of finding the missing Brit alive. His stag do friends spent the weekend holed up in a hotel in central Lisbon.

Leading state broadcaster said the police had reached the conclusion that the suspect had pushed the missing man off the boat while he was “unconscious and without a life jacket.” There is no suggestion the act was a deliberate attempt to do the Brit any harm, but if the allegation is proved it will leave the Brit facing a possible manslaughter charge if a body is found.