New Prime Minister Gordon Brown has been challenged on the constitutional changes he is proposing by Scottish Roman Catholic Cardinal Keith O’Brien – because he has not included mention of the repeal of the Act of Settlement, which ensures that only a Protestant can take the British throne.

“I am deeply disappointed at the statement from Gordon Brown”, the Cardinal, a controversial figure for his interventions on abortion and other issues, declared earlier this week.

He continued: “I remain deeply concerned that the ‘Act of Settlement’ will continue to exist and believe it constitutes state-sponsored sectarianism.”

The Cardinal said that “I have been happy to note the recent remarks by Scotland’s new First Minister, Alex Salmond that the Act of Settlement should be removed.”

The Catholic Church, traditionally a bastion of Labour support, has enjoyed a surprising renewal of relations with the Scottish Nationalists (SNP), and Mr Salmond has been supportive of church schools which others – both religious and non-religious – criticise.

Cardinal O’Brien declared: “I wrote to Gordon Brown in April 2006 following comments he made on the role of the Prime Minister in the selection of Church of England bishops to say that the terms of the Act of Settlement were anachronistic and that it was ‘an outstanding example of bigotry and sectarianism in the United Kingdom’. I urged him to consider these views but did not receive a reply.”

When the Cardinal first wrote to Mr Brown, he was Chancellor of the Exchequer. It is traditional for the chancellor to stay out of constitutional debates.

Then PM Tony Blair, who is very sympathetic to the Catholic cause, and who is frequently reported in the media to be on the verge of converting to the Roman church, is known to be sympathetic to ending the Act of Settlement.

But his advisors were strongly of the opinion that opening up fresh constitutional questions would be unwise because he was due to leave office.

His successor, Gordon Brown, is, like Blair, a member of the Christian Socialist Movement (CSM). Brown, however, is a Presbyterian, and his father was a minister of the Church of Scotland. Neither is keen to use the word ‘socialist’.

Mr Brown is known to have ecumenical sympathies, and in addition to many advisors who do not hold religious beliefs, he has been willing to listen to Chief Rabbi Jonathan Sachs, and progressive US evangelical social activist Jim Wallis.

The Act of Settlement ensured the succession to the throne by the heirs of the Protestant Electress Sophia of Hanover, a granddaughter of James I. It excludes Roman Catholics, Muslims and other non-Protestants (including humanists and non-believers) from succeeding to the throne.

From the perspective of Britain’s largely unwritten constitutional arrangements, the etablished Church of England is seen as Protestant, though many of its members and theologians describe it as “both Catholic and Reformed”.

The Church of Scotland (Presbyterian) has official recognition from the monarch north of the border, though it is not a formal state church.