Back in 2007 he converted to Catholicism and as Prime Minister he introduced civil unions for same-sex couples.
Now Tony Blair is going even further, backing the legalisation of same-sex marriages in Britain.
This is in open defiance to the Pope and Catholics who are vehemently opposed to the proposal that was made by Britain's Conservative PM, David Cameron.
The proposal was also met with strong disapproval from leaders of the Anglican Church, despite the fact that many of their vicars and deans are in favour of the change.
Last Sunday, a letter from two archbishops was read out to Catholic congregations in England and Wales, explaining that the new law would undermine the institution of marriage and the family.
Despite this, the Independent on Sunday revealed, Blair has allegedly told friends he "strongly supports the Prime Minister's proposal."
Blair who was responsible for the introduction of civil partnership laws for same-sex couples and for reducing the age of consent for homosexuals to 16, had kept out of the same-sex marriage debate until now.
Despite the opposition shown by the clergy, Cameron and some of his most conservative ministers are still in favour of legalising same-sex marriage.
Lynne Featherstone, the equalities minister who will launch a public consultation on the issue this month, stated that marriage is "owned by the people" not by the church.