Catholics and first-born daughters to be allowed on throne in massive reform to constitution

Britain's constitutional laws could be reformed to give women equal rights as men to ascend the throne, and to allow Roman Catholics to rule.

Downing Street is deciding whether to alter the 300-year-old Act of Settlement governing the succession.

The plans are being proposed by Labour MP Chris Bryant, who has been put in charge of reviewing the constitution by Gordon Brown.

The 1701 Act of Settlement bars all Catholics and anyone married to a Catholic from reigning, and forces any monarch to reject Catholicism.

It also reinforces primogeniture, which dictates that males succeed to the throne before females. If this is changed, Prince William's first child would be his heir, regardless of sex.

Critics have long argued about the Act's relevance in the 21st century. Even the Queen is said to be 'sanguine' about suggestions of reform.

Mr Bryant, a former priest, recently argued that the laws are almost certainly a breach of human rights. He confirmed that he had submitted his proposals to No 10, but would not be drawn on their contents.

Downing Street yesterday said it was willing to 'consider the arguments', but insisted it was not yet Government policy. But Mr Brown is reported to be keen to pass the legislation quickly if it wins a fourth term in office.

A change in the males-first succession law would put the Princess Royal ahead of younger brother Edward, right, in line to the throne. His daughter Lady Louise  - pictured in his arms - would also be above her own younger brother James

In a pamphlet published last week by the Local Government Association, Mr Bryant argued that forcing the monarch to swear to preserve the Church of England and uphold the Protestant line of succession almost certainly represented a breach of human rights.

And he suggested it was 'inconceivable' that, should Prince William have a daughter before a son, she would not be the one to eventually take the throne. Sweden, he pointed out, has already changed its law to deal with such a situation.

In Britain, the line of succession places Princess Anne, the Queen's second child, below her brothers Andrew and Edward - 10 and 14 years her junior respectively.

More recently Lady Louise Windsor, the four-year-old daughter of Edward and his wife Sophie, was placed lower in the line of succession than her younger brother, one-year-old James.

The MP, who is a former priest, also argued for reform of the constitutional role of the Church of England and of the 'strange' powers of the Privy Council.

A future coronation would have to be 'radically different' from that of the present Queen's, he suggested, 'to recognise the monarch's role in protecting the freedoms of all citizens and subjects, rather than just the Church of England'.

Liberal Democrat equalities spokeswoman Lynne Featherstone today welcome the 'overdue' move.

She said: 'Whilst the hereditary principle itself is obviously still a bit dodgy, at least this modernisation ends the outrageous discrimination against Catholics and women.

'It was completely unfair that Prince Edward's daughter was bumped down the list of succession in favour of her younger brother,' she said.

'As we chip away at the established order, the message will eventually get through that men and women are equal.'

Tory justice spokesman Nick Herbert said: 'Gordon Brown needs to explain why he thinks this is a pressing issue in the current economic circumstances.'