In the week of the Royal Wedding, a centuries-old law banning British monarchs from becoming or marrying a Catholic is sparking a row in the United Kingdom.

London’s Daily Telegraph reported on April 25 that plans to abolish the 1701 Act of Settlement have been ditched because of "significant objections" from the Church of England.

Now the First Minister of Scotland, Alex Salmond, has written to the British Government asking for urgent clarification.

"I recently wrote to the Prime Minister (David Cameron) calling for the abolition of all discrimination contained in the Act of Settlement, including its blatant discrimination towards Catholics, which is completely unacceptable in a modern society. I am deeply concerned at these reports that this much-needed and long overdue reform has been shelved by the UK Government," Salmond wrote.

There is no similar prohibition on the British royal family marrying members of other faiths such as Islam or Judaism, or those who are agnostic or athiest. Anglicanism is still the state religion in England and the monarch is called the "Supreme Governor" of the Anglican faith.

A spokesman for the British Government told the Telegraph, that the government “accepts there are provisions (in the Act) which could be discriminatory."

However, he added, the process of amending the law is “a complex and difficult matter that requires careful and thoughtful consideration” because it effects succession to England’s throne.

A Church of England spokesman expressed similar concerns. He said that the anti-Catholic prohibition “inevitably” looks outdated.

“But if the prohibition were removed the difficulty would still remain that establishment requires the monarch to join in communion with the Church of England as its Supreme Governor and that is not something that a Roman Catholic would be able to do consistently with the current rules of that Church,” the spokesman told The Telegraph.

The Act was originally passed to prevent the descendants of the Catholic King James II from ascending the throne. He was deposed in the 1688 "glorious revolution" by supporters of the Protestant William and Mary.  Mary was the eldest Protestant daughter of James II and was married to William of Orange, who later became William III.

In recent years, the Act has effected several members of the British royal family.

In 2001, Lord Nicholas Windsor, the youngest son of the Duke and Duchess of Kent, permanently forfeited his right to the royal succession by converting to Catholicism.

In 2008, Autumn Kelly, the Canadian fiancee of the Queen's grandson Peter Philips, converted from Catholicism to Anglicanism, thus preserving her husband's chances of becoming king.

The present second-in-line to the British throne, Prince William, will marry Kate Middleton on April 29 at a Anglican service in London's Westminster Abbey.