A senior Roman Catholic bishop has launched a fierce attack on Prime Minister Gordon Brown over his failure to pledge reform of Britain’s anti-Catholic laws.

In a strongly-worded letter to him at Downing Street, the Right Rev Joseph Devine, Bishop of Motherwell in Scotland, accuses the Prime Minister of compromising his beliefs in justice, virtue and respect.

He accuses Mr Brown of “surrendering” to anti-Catholic lobbyists who are resisting repeal of the Act of Settlement of 1701 and says he has “broken faith” with the nation’s five million Catholics.

He demands that before the next General Election, the Prime Minister announce “a firm timetable” to reform the Act of Settlement.

The 1701 legislation, introduced to ensure the Protestant succession to the British throne, enshrined discriminatory anti-Catholic measures into British law. It helped lead to the union of England and Wales with Scotland, and its measures apply throughout the Commonwealth.

Under one of its provisions, the heir to the throne can become monarch if he marries a Scientologist, Muslim, Buddhist, Moonie or even a Satanist, but not if he or she marries a Roman Catholic.

Although the Act does not affect directly the lives of the 800,000 Catolics in Scotland and four million-plus in England and Wales, it is regarded widely as an anomaly in an era when the removal of discrimination against homosexuals, non-Christian religions and other minority groups is seen as a priority by Labour.

In Scotland, where sectarianism has been described as the nation’s “shame”, it is a particularly sensitive matter as the Act of Settlement is seen as legitiming anti-Catholic prejudice.

But its repeal would be a complicated and time-consuming matter. One complication is that every Commonwealth country would have to repeal it individually or risk splitting the monarchy. If Prince William married a Catholic, he could only become King in those countries that had repealed the Act.

In a letter to the Prime Minister, Bishop Devine says that following public appeals from the Cardinals of England and Wales and Scotland, the leaders of all political parties in the Scottish Parliament with the exception of Labour’s Wendy Alexander have agreed to support the Church’s campaign to have the act repealed.

Bishop Devine says the Church is now looking to the Government to announce “a firm timetable to reform the Act of Settlement and pledge that Catholics will no longer be victims of state sponsored sectarianism.” He warns: “Nothing less will do.”

Giving an indication of the extent of Catholic anger about the Act of Settlement, seen as a symbol of lingering anti-Catholic prejudice in Britain, Bishop Devine notes that at the start of his premiership, Mr Brown emphasised his “integrity, honour and serious moral purpose.”

He says: “[This] led many of us to have justifiable hopes, with your encouragement, of a new kind of politics where justice, truth and defence of human rights would be paramount virtues in government.”

Turning on the Christian credentials of the Prime Minister, a son of the Presbyterian manse, he then describes it as “a fascinating irony” that someone from a devout Christian background, and identified more than most modern politicians with firm Christian convictions, “should be seen to compromise your beliefs of virtue, respect and justice for all by apparently surrendering to anonymous pressure groups and individuals who are determined to uphold the notorious anti-Catholic provisions in the Act of Settlement.”

Claiming it was Mr Brown’s acknowledged intention to overturn the legislation, Bishop Devine alleges that at the eleventh hour, Mr Brown was persuaded to change his plans “by virulently anti-Catholic antagonists.”

If this was not so, the decision to retain the anti-Catholic legislation was his alone, the Bishop says. “I would prefer to believe that you allowed your honourable and honest intentions to be thwarted by people of doubtful intent.”

He continues: “Five million British Catholics who looked to you as their Prime Minister to protect their hard won rights and ensure they had equality before the law understandably feel you have broken faith with them. Under your premiership and government they continue to suffer from legislation designed to offend, malign and marginalise them.”

That the Labour Government should saction the continued discrimination against Catholics “is an affront to civilised society and serves only to encourage the suspicion that the demons of our past remain at large where we might least expect to find them,” says Bishop Devine. “I have the depressing feeling that if this legislation had discriminated against other sections of society and religious groups there would be justifiable outrage no doubt with government quite properly in the vanguard of the campaign to overturn such a prejudiced Act.”

Earlier this year, Bishop Devine wrote to all party leaders in Scotland describing the “deep hurt and dismay” among Catholics over the failure to repeal the Act.