Conservative MP Patrick Mercer has refused to discuss claims he called David Cameron a "despicable creature without any redeeming features".
Several newspapers have reported that the former Army officer made a series of disparaging remarks about the prime minister during a private function.
He allegedly predicted the PM would be ousted in a backbench coup next spring.
But when asked about the reports on BBC Radio 5 Live, Mr Mercer said: "I am not going to discuss it."
The MP for Newark was forced to resign as Mr Cameron's shadow homeland security spokesman in 2007 after making comments about race in the Army which his party leader called "unacceptable".
The Sunday People and Sunday Mirror both carried reports about comments allegedly made by Mr Mercer.
He was said to have told a fellow guest at the function he would "rather take a beggar off the street" and put them in Downing Street than have Mr Cameron there.
He also reportedly called his party leader "the worst politician in British history since William Gladstone".
Asked about a possible backbench uprising against Mr Cameron, Mr Mercer is alleged to have said: "He'll go in the spring. He'll resign in the spring."
During an interview on the BBC's Pienaar's Politics programme, Mr Mercer repeatedly refused to be drawn on the claims.
He has acknowledged having "a conversation with a number of people" at the event, but said the recordings had been obtained by "subterfuge".
He denied they backed up the claims he had insulted Mr Cameron and said he was consulting with his lawyers.
The Conservative Party said it had no comment, but added that such remarks did not necessarily merit disciplinary action.
There was no comment from Downing Street.
Mr Mercer, who served with the Army in Northern Ireland and Bosnia, is a known critic of Mr Cameron and was among backbenchers who rebelled last month over a referendum on European Union membership.
After leaving Mr Cameron's shadow cabinet in 2007, he went on to serve as an adviser to Labour security minister Lord West.