The SNP has stepped up calls for peers convicted of a criminal offence to be thrown out of Parliament amid reports ministers are considering such a measure.

Politicians from across the political spectrum have complained that peers should not be allowed to keep their seats in the House of Lords if they have committed crimes.

There was outrage when Lord Watson, the ex-Labour peer, was allowed to remain a member of the Upper chamber despite serving time for fire raising. Other peers to have kept their titles include Lord Archer, who was jailed for perjury.

Critics of the current system also point out that MPs have to give up their seats in the House of Commons if sent to jail for more than a year.

It is thought the new measure could be included in the Queen's speech this year. Under the plans it is thought peers themselves would be given the power to expel members who have been convicted of a serious offence.

Proposals included in the draft House of Lords Reform Bill would allow convicted peers to be suspended.

However, pressure is growing for them to be expelled.

It has traditionally been difficult to remove peers from the House of Lords, in part to remain independent and immune from political pressure.

Pete Wishart, the SNP Constitutional Affairs spokesman, said the announcement last week Fred Goodwin, the ex-RBS boss, had been stripped of his knighthood had shone a light on the conduct of those given Honours.

"It is ridiculous that peers, convicted and imprisoned for serious criminal offences can retain, not just their title, but their seat and privileges in the House of Lords," he said.

"In circumstances where an MP would be disqualified and lose their seat, for Lords it really is a case of one law for them and another for the rest of us."

Lord Watson was expelled by the Labour party seven years ago after his conviction, but remains a member of the House of Lords.