MSPs are to be canvassed on the idea

Mike Russell, the Scottish National Party's business manager, said the little-known 1701 Act of Settlement was "institutionalised discrimination" with no place in the 21st Century.

The Act, passed by the English Parliament, bars royals from becoming King or Queen if they "profess the popish religion or shall marry a Papist".

Only Westminster can abolish the law, but Mr Russell wants the Scottish parliament to lobby for the change.

He said he would either prepare a motion for debate in the Scottish Parliament, or ask a question in the House. He intends to act as soon as he has consulted fellow MSPs and expects cross-party support.

'Time to end discrimination'

"We need to get rid of institutionalised discrimination. This Act is archaic and nobody pays much attention to it these days - few people have even heard of it," he said.

"But it means anti-Catholic discrimination is at the heart of our constitution, and I suspect it applies to all people who are not of the Protestant faith such as Muslims and Hindus.

"It's time to get rid of it."