Tony Blair received a tough dressing down from Pope Benedict XVI during his audience with the pontiff yesterday, not only over the war in Iraq but also over legislation passed during Mr Blair's ten years in power on abortion, gay adoption and stem cell research.

Some newspapers at the end of last week carried reports predicting that Mr Blair would convert to Roman Catholicism after leaving office and that the Pope would give the conversion his blessing during their farewell meeting at the Vatican on Saturday.

However the Vatican said after the meeting that the pontiff and Mr Blair had had a "frank exchange" on "particularly delicate subjects", which is Vatican-speak for downright disagreement. Italian reports said the Pope had criticised UK laws allowing greater stem cell research on human embryos, easy access to abortion, same-sex marriages, and adoption by gay couples.

Today, the Pope made an enigmatic reference to "true conversion" in his midday Angelus prayers. Addressing English speaking pilgrims on St Peter's Square he said: "Today, as the Church celebrates the birth of St John the Baptist, let us ask for the gift of true conversion and growth in holiness, so that our lives will prepare a way for the Lord and hasten the coming of His Kingdom."

During the public part of the encounter the Pope and Mr Blair were all smiles yesterday. The Pope wished Mr Blair well on his plans to work for Middle East peace and inter-faith dialogue. The two men met privately for 25 minutes and then - in an unusual gesture - were joined by Cardinal Cormac Murphy-O'Connor, the Archbishop of Westminster.

A Vatican communiqué made no mention of conversion but described the audience as "a normal meeting between the Pope and a government leader."

The Vatican statement, issued after the talks with the Pope Benedict and a separate meeting with Secretary of State Cardinal Tarcisio Bertone, said there was a "frank" assessment of the international situation, including such "delicate" themes as the Middle East conflict and the future of the European Union.

This referred to the deep Vatican opposition to the war in Iraq, first expressed to Mr Blair by the late John Paul II and reiterated since. It also referred to Pope Benedict's disappointment over Mr Blair's failure to back the Vatican's campaign to have a reference to Europe's Christian roots and values inserted into the EU Constitution.

In an interview with The Times published on Saturday Mr Blair admitted the issue of his religious beliefs was complex and that he was nervous about discussing his faith with the Pope. "It's difficult with some of these things," Mr Blair said. "Things aren't always as resolved as they might be." A spokesman for the Prime Minister repeated the official line that "he remains a member of the Church of England."

Cherie Blair is Roman Catholic, the couple's children have attended Catholic schools and Mr Blair has for years regularly attended Catholic services. He is reliably said to have received Communion at the hands of John Paul II in the papal chapel.

Some commentators saw the fact that the Blairs gave Pope Benedict three period photographs of Cardinal John Henry Newman, a famous nineteenth century British convert to Catholicism, as a symbolic gesture signalling Mr Blair's own imminent conversion.

On the other hand Vatican sources point out that as a young theology student at Freising the Pope made a special study of Cardinal Newman, writing his doctorate on Newman's theology of conscience, and has supported moves to make him a saint.

Last month May Father Michael Seed, a Westminster priest close to the Blairs, predicted that Mr Blair would become a Catholic. But he later told The Times he did not know if Mr Blair would ever be received "formally" into the Roman Catholic Church.

There has never been a Catholic Prime Minister in Britain, and Mr Blair would have been aware that to convert could have been at odds with his role in choosing Church of England bishops.

The official entourage included Francis Campbell, the British Ambassador to the Holy See, Lady Carla Powell, the Italian born sister-in-law of Mr Blair's chief- of-staff Jonathan Powell, and - mysteriously - the French billionaire businessman Bernard Arnault, head of the luxury goods firm LVMH, who is a Catholic.

Four years ago Mr Blair was given a dressing down by Pope John Paul II, who warned him not to invade Iraq. The Vatican feels that events since the late Pope's views were brushed aside have proved him right.