The leader of the Catholic Church in Scotland has called for Catholics to be allowed to rise to the monarchy.
The cardinal wants Catholics to be allowed to marry royalty
Cardinal Keith O'Brien was speaking at a summit on Scottish Executive plans to tackle religious bigotry.
Cardinal O'Brien described the Act of Settlement, banning Catholics from the throne, as "hurtful" and discriminatory.
The Orange Order in Scotland dismissed the call, claiming the act guaranteed everyone's religious liberty.
The cardinal said: "It's a matter of regret surely that had Mrs Parker Bowles been a Catholic, Prince Charles would have lost the right to succession to the throne and similarly if they had been going to have children they would have been excluded from the right of succession and that's hurtful.
"Here in Scotland one-in-five of the population are equally loyal Catholics.
"So why should Prince Charles, or any heir to our throne, be able to marry not just someone of the Anglican faith, but someone who is a Muslim or, but not a Roman Catholic."
The grand master of the Grand Orange Lodge of Scotland, Ian Wilson, said he recognised the situation may be hurtful to Catholics but that this sort of "institutionalised sectarianism" was a historical fact.
Mr Wilson said: "I wouldn't have thought it was all that unusual for a Protestant country like this to have a Protestant monarchy.
"Prince Charles should marry who he is in love with and I've absolutely no problem with that - the difficulty is that Prince Charles isn't like you and I, he has a constitutional role.
"The settlement is there for good historical reasons and particularly we see it as a guarantee of our religious liberties.
"Having a Protestant monarchy, under the constitutional arrangements that we have, guarantees everyone's religious liberty."
Cardinal O'Brien said he realised the act was a matter for Westminster, but he urged the Scottish Executive to lobby for the law to be repealed or amended.