Stripping Watson of his title would require an act of parliament

Watson said he would resign from the Scottish Parliament after he pleaded guilty to trying to start a fire at an Edinburgh hotel last year.

An act of parliament would be needed to change the law if Watson were to be stripped of his title.

But the Lib Dems said such a move would be "appropriate".

Watson, the MSP for Glasgow Cathcart, admitted setting fire to curtains at the Prestonfield Hotel following the Politician of the Year awards in November.

The 56-year-old's future in the Labour Party will be decided after he is sentenced in three weeks' time.

If he has been fit to resign from one law-making body, then I think it would be most appropriate for him to resign from the other Mike Rumbles Lib Dem MSP

Lib Dem MSP and former convener of the standards committee, Mike Rumbles, said it would be "appropriate" and "consistent" for Watson to be stripped of his title.

Mr Rumbles said: "If he has been fit to resign from one law-making body, then I think it would be most appropriate for him to resign from the other.

"This would be most consistent. He felt it right to resign from the Scottish Parliament so as the House of Lords is a similar law-making body, it is completely inappropriate for him to resign from one and not the other.

'Put this right'

"It is regrettable, but it is an issue for Westminster."

Mr Rumbles said he believed anyone convicted of a serious crime and of endangering lives should have their right to legislate removed.

"This would take an act of parliament to change the law," Mr Rumbles went on.

"The House of Commons should take action to put this right."

Scottish National Party MSP Alex Neil said criminals were not allowed to sit in the Commons or Holyrood, and he argued the same should apply in the House of Lords.