Three MPs who "got drunk" on a plane to Gibraltar could be kicked out of a parliamentary Armed Forces scheme because of bad behaviour, it was suggested on Thursday night as two Tories were also accused of drinking too much on the trip.

       Charlotte Nichols, a Labour MP, and the SNP's David Linden and Drew Hendry, could lose the right to go on parliamentary trips to military bases after Ben Wallace, the Defence Secretary, wrote to their party leaders about their "unacceptable" behaviour.

       It was claimed the three "drank heavily" on a British Airways flight to Gibraltar, where they and 11 colleagues were meeting British troops on a visit to mark Armistice Day.

       Ms Nichols returned to London on Tuesday, citing ill health, but Mr Linden and Mr Hendry remained on the visit until their scheduled return on Thursday. All three insist they were not drunk on the plane but do not deny drinking any alcohol.

       A shadow minister said on Thursday that the party's chief whip would "look into" Ms Nichols' involvement in the incident, but Labour sources played down the idea that she would face any disciplinary action and pointed to her health concerns as a mitigating factor.

       James Gray, a Tory MP who chairs the Armed Forces Parliamentary Scheme, which organised the trip, will decide on Monday whether the MPs should be allowed to stay in the group and attend future visits.

       "I will see them all on Monday and they can tell me their side of it," Mr Gray told The Telegraph. "If the trustees or I come to the conclusion that one or another of them behaved wrongly, then I would suggest they might not be gaining much from the course and might be better to do something else. It may be that we suspend them for a short time."

       His intervention came as it was claimed that two Conservative MPs, Christian Wakeford and Ben Everitt, had shown disrespect to the military before Armistice Day by going out drinking in Gibraltar until the early hours of Wednesday morning. The Conservative Party did not deny the claims.

       As the row over the trip escalated, Tory and SNP sources accused each other of attempting to use accusations of drunkenness to deflect from criticism of their own parties.

       An SNP spokesman accused Mr Wallace of "dragging our Armed Forces into silly political point-scoring", and described the claims about Mr Linden and Mr Hendry as "a botched attempt to divert media attention from the Tory sleaze scandal".

       Reacting to claims that Conservative MPs had also been drinking, a Tory source said: "This is quite clearly a desperate attempt by those involved in the flight incident to deflect attention away from their behaviour."