Fr Sean McManus, president of the Capitol Hill-based Irish National Caucus group, last week launched the campaign to repeal the "archaic" 1701 British Act of Settlement.

The Act of Settlement decrees that only a Protestant can succeed to the British throne and that if the monarch becomes a Catholic, or marries a Catholic, they forfeit the throne and "the people are absolved from their allegiance".

McManus told the Sunday Tribune: "While this absurdly anachronistic law may mean little to the average Englishman in the street, it has always been of the utmost importance to Protestant/ Unionist/Orange extremists in Northern Ireland.

"It provides the ideological and philosophical underpinnings for their bigotry and sectarianism. If a Catholic by law can't get the top job, then Catholics are inferior to Protestants.

"Therefore it's okay to discriminate against them."

McManus claims that if the US constitution had a provision forbidding AfricanAmericans from being president, it "would have stoked the flames of racism and the sick ideology of white supremacy".

The campaign has now issued each member of the US Congress with a 'Roll Call on the Act of Settlement, 1701', on which they can call for the repeal of the act and support the Irish peace process.

Above the space on the Roll Call form, where each Senator signs their support for the campaign, a statement reads "God bless America and God save Ireland".

The Irish National Caucus was founded by McManus and is best known for its work in lobbying for the MacBride Principles, a corporate code of conduct for US companies doing business in Northern Ireland, in the 1980s and 1990s.

In 2001, a backbench bill proposed in the House of Commons by Hull MP Kevin McNamara seeking an end to the bar on Roman Catholics succeeding the British throne came under fire from DUP leader Ian Paisley.

Speaking of his proposal at the time, McNamara claimed: "I am looking, in this bill, to strike at discrimination and intolerance in our society. I am looking to assist the process of inclusion."

However, Paisley accused McNamara of trying to "underwrite the constitution" and said the link between religion and the monarchy had served the country well.

He argued that several other European countries, such as Sweden and Spain, kept the constitutional link between religion and monarchy.

Paisley was unavailable for comment when contacted by the Sunday Tribune this weekend, but a DUP spokesman indicated that his position on the 1701 act had not changed.