Sir Malcolm Rifkind has said a snap general election would be "a constitutional outrage".
The Queen should stop a snap poll, joked Sir Malcolm
The Tory former foreign secretary said Prime Minister Gordon Brown will have "lost his political marbles" if he goes to the country this autumn.
He said governments with a working majority in the House of Commons should serve a full term.
Sir Malcolm was speaking at a fringe meeting at the Conservative Party Conference in Blackpool.
Mr Brown is thought to be contemplating an October poll in order to capitalise on Labour's lead in the opinion polls.
But Sir Malcolm was one of three MPs defeated in the Tory leadership campaign by David Cameron in 2005.
He told the meeting: "I think to contemplate a general election two years after the last general election when you have a healthy working majority in the House of Commons is a constitutional outrage."
He joked: "I just wish the Queen would say 'you cannot have one'. It would probably be the end of the monarchy but what a way to go!"