Royal succession rules banning Roman Catholics from succeeding to the throne should be scrapped, the Prime Minister has said.
David Cameron said Catholics should be able to become King or Queen, or marry the heir to the throne, but warned that changing the 1701 Act of Settlement would take time.
He has said he would also like to scrap the law giving preference to male heirs, which has come under increased pressure with the upcoming wedding of Prince William and Kate Middleton.
Mr Cameron and Deputy Prime Minister Nick Clegg are in discussions with other Commonwealth leaders about how to secure a change across the nations where the Queen is the monarch.
He told BBC Radio 4's Today programme: "I think that it's right to discuss both sets of changes but I think we have to recognise that the Queen is not only the Queen of the United Kingdom but also many other jurisdictions as well.
"So discussions have to take place between the UK Government and other governments around the world and also with the Palace in order to bring this about."
He added: "In principle I think both changes should be made, in principle I'm of that view. But it will take time because it's not just our decision, it's the decision of others as well."