Catholic Church to join Tony Blair "within weeks".
He decided to remain 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.
Mr Blair's conversion will be controversial in the Catholic community because as an MP Mr Blair voted for abortion at up to 24 weeks which was publicly condemned by the late Cardinal Thomas Winning of Scotland. He also supported civil partnerships for homosexual couples.
All four of the Blair children were baptised as Catholics and the family used to attend Mass at St Joan of Arc Church in Islington when he was opposition leader.
After becoming prime minister he stopped doing so in public on the instructions of the then leader of Catholics in England and Wales, the late Cardinal Hume.
But he continued to attend private masses with Fr Michael Seed...
The Tablet reported that Mr Blair was invited to be received into the Church in Rome but his advisers discouraged the idea, believing it might seem like Catholic triumphalism.
I don't claim to be well versed in sky pilot matters but it seems obvious that Tony Blair put his ambition and desire to be Prime Minister ahead of his belief that the Catholic church is the one true way to salvation. Now if you believe that kissing the right ring gives you access to everlasting pleasure in heaven then risking losing that to continue to be Prime Minister (and does anyone really believe he would have been chucked out for being a left footer) seems to be a pretty bad bargain. Aren't avarice and vanity sins in Rome?