Sir Malcolm Bruce made the remark as he defended the actions of ex-Scottish Secretary Alistair Carmichael.
Mr Carmichael is facing calls to resign after admitting he backed the leaking of a memo during the election campaign incorrectly suggesting Nicola Sturgeon wanted David Cameron as prime minister.
Speaking to the BBC Radio 4 Today programme, Sir Malcolm, a former deputy leader of his party, said: “If you’re suggesting every MP who has never quite told the truth or indeed told a brazen lie, including ministers, including Cabinet ministers, including prime ministers, [should resign] we’d clear out the House of Commons very fast, I would suggest.”
Asked if he was suggesting that lying in public life is widespread, Sir Malcolm replied: “No. Well, yes.
“I think the answer is lots of people have told lies and you know that to be perfectly true.”