Blair 'planning to become a Catholic after he quits No 10'

His long- awaited formal switch to the faith of his wife and family will come shortly after he surrenders office, it is claimed.

Mr Blair's decision to formalise his Catholic beliefs was revealed by Father Michael Seed, who is regarded as unofficial chaplain to Westminster and is a regular visitor to Number Ten.

Last year, Cherie Blair praised Father Seed, a leading cleric at Westminster Cathedral, for his "ability to reach out to all kinds of people, whether it is the homeless on the streets to the people in the highest places in the land, including even in Downing Street".

Asked to elaborate yesterday, Father Seed, usually known for his openness with the media, said: "I'm afraid I can't say anything."

Mr Blair has long been expected to complete his conversion after leaving Downing Street.

He has regularly attended Catholic services in recent years, both with his family and alone.

Mr Blair has also visited Pope Benedict XVI and his predecessor John Paul II in Rome.

While opposition leader in the mid-1990s Mr Blair often took communion with his wife and children at a Catholic church in Islington in London, which is seen as a signal he is totally loyal to the faith.

However, he stopped doing so in public on the instructions of the then leader of Catholics in England and Wales, the late Cardinal Hume.

Mr Blair has not been seen in a church of his professed Anglican faith except on official occasions.

He is widely considered to have remained an Anglican because of the potential complexities of conversion while in office.

Some lawyers believe the 1829 Emancipation Act, which gave Roman Catholics full civil rights, may still prevent a Catholic from becoming Prime Minister.

Clauses in the Act state that no Catholic adviser to the monarch can hold civil or military office.

Despite his apparent commitment to the faith, Mr Blair has also frequently clashed with Roman Catholic leaders, particularly over his liberal policies on gay rights and abortion.

In recent months, the leader of Catholics in England and Wales, Cardinal Cormac Murphy-O'Connor, has been severely critical of the Sexual Orientation Regulations.

The Government claims the rules will protect homosexuals from discrimination.

But Catholic leaders say they will force Christians to act in conflict with their principles.

The Cardinal has threatened to close Catholic adoption agencies if they are forced to place children with gay couples.

If Mr Blair is to convert formally, he will have to undergo a course of instruction, which is likely to be conducted by Father Seed.

To be received officially into the Church, he will be expected to take part in a service of baptism, followed by confirmation and Holy Communion.

Downing Street refused to be drawn on Mr Blair's intentions yesterday. A spokesman said: "This story is always circulating in one form or another.

"The Prime Minister remains a member of the Church of England."