Canadian Prime Minister Paul Martin, his aide and three politicians of Punjabi origin are at the centre of a favour-seeking controversy.

Gurmant Grewal, the Conservative MP from Surrey in British Columbia, has handed over to the Royal Canadian Mountain Police (RCMP) secret tapes of conversations he had with senior Liberals seeking rewards in exchange for helping them keep the government from falling.

Grewal has made public several recordings and transcripts of conversations with Martin's chief of staff Tim Murphy, Health Minister Ujjal Dosanjh and Sudesh Kalia, a friend of Grewal and a Liberal Party member.

The tapes show that the prime minister was in the loop as Murphy negotiated with Grewal and his wife Nina, also an MP, to either switch parties or refrain from the May 19 vote in parliament.

The Liberals eventually won the crucial vote only when Speaker Peter Milliken broke a 152-152 tie.

Dosanjh had denied any dealings when Grewal released eight minutes of the tapes just before the vote.

He claimed it was the other way around, in that he was approached by an intermediary for the Gerwals with an offer that they would cross the floor "provided she gets a senate seat and he gets a cabinet post", the National Post quoted him as saying.

"I'm actually offended that Grewal would go to the length of approaching us making totally inappropriate demands," Dosanjh said, "and when he was rebuffed time and time again he will try and come over and talk to Tim Murphy and show him how great a standing he had in the community ... therefore he should be rewarded right away and in a very significant way for crossing the floor."

Kalia, the go-between, appeared on national television and claimed the same: "He (Grewal) said 'If you can, if you know someone, if you can talk, I'm willing.' So I talked to Ujjal on behalf of Grewal." 

The Liberals now charge that the tapes have been altered.

"The transcripts don't look manipulated or doctored but definitely the tapes have disconnected and interrupted audio ... at the same time there is no explicit offer (from the Liberals) ... it's going to be really hard for him (Grewal) to prove how low the Liberals can stoop, if that's what he wants to...," Yudhvir Jaswal, a Punjabi radio and Hindi television host for Asian Connection, a community media company, told IANS.

Jaswal said he has heard all the tapes and corresponding transcripts made public by Grewal.

Grewal's message on his website said he welcomed any investigation deemed appropriate by the RCMP and that he would not have any further public comment on the matter.

RCMP's involvement could lead to a criminal investigation and federal ethics commissioner Bernard Shapiro may also investigate the issue, media reports say.