Advisers to the Pope are starting to regret that he accepted an invitation to visit Britain this September after official papers emerged that suggested he should be asked to open an abortion clinic, bless a gay marriage and launch a Benedict-branded condom range.

The document also suggested that the National Anthem be changed, from God Save the Queen to God Save the World.

As the Foreign and Commonwealth Office was forced into a rapid damage-limitation exercise with an official apology for an “unacceptable” document, sources told The Times that the entire visit could now be in jeopardy.

The document was drawn up by the Foreign Office as part of a briefing pack and sent to officials across Whitehall.

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It also suggested that Benedict XVI could demonstrate a hard line on child abuse by “sacking dodgy bishops” and launching a helpline for abused children.

The Government’s papal visit team document also recommended that he sing a song with the Queen for charity and apologise for the Spanish Armada.

A Foreign Office spokesman said that the paper was flagged as unacceptable as soon as it was seen and Francis Campbell, the British Ambassador to the Holy See, has met Vatican officials to apologise.

Some senior Catholics in Britain attempted to downplay its significance but The Times has learnt that the document has caused enormous anger in Rome. It is regarded as just the latest, but by far the most serious, in a series of anti-Catholic episodes emanating from the UK that threaten to cast a cloud over the Pope’s four-day visit to England and Scotland.

Coming on top of comments about him over paedophile priests and threats by militant secularists such as Richard Dawkins that the pontiff could face arrest, in spite of enjoying diplomatic immunity as head of state, it is leading some Vatican advisers to question why he is coming to a country where the public mood even at the centre of government seems so hostile.

The document could also do lasting damage to decades of hard work building strong relations between the British Government and the Holy See, as well as to the reputation of the Foreign Office, an institution once known for employing the highest calibre of staff.

A source told The Times that the issue was being dismissed by many as a joke that went wrong but of more serious substance was that it could be written and disseminated at all. The source questioned what the consequences would be if such a document were written by a British government official about the head of an Islamic country.

Officially, though, the line from Church and state was to downplay its impact.

Father Federico Lombardi, the Pope’s spokesman, said: “I am aware that the Foreign Office has made a statement on this matter and I am aware of the contents of the memo.

“We are not saying anything else as there is no need to ruin the good relations between the British Government and the Vatican.”

A Foreign Office spokesman said that David Miliband, the Foreign Secretary, was aware of the document and “appalled” by it.

The ideas in the paper, entitled The Ideal Visit We Would Like to See, were drawn up by what the Foreign Office described as “a group of three or four junior staff in a team working on the papal visit”.

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It was attached as one of three “background documents” to an e-mail headed Policy Planning Ahead of the Pope’s Visit, dated March 5, which invited officials to attend a meeting.

The author of the e-mail, said to be an Oxbridge-educated junior civil servant in his twenties, admitted that some of the ideas were “far-fetched”. Recipients included Nicola Ware, a senior Foreign Office official, as well as Downing Street, the Department for International Development and the Northern Ireland Office.

One suggested that Pope Benedict should be persuaded to spend a night in a council flat in Bradford and “do forward rolls with children to promote healthy living”.

The memo also featured a list of “positive” people who could be associated with the trip, including Tony Blair and Susan Boyle, the Britain’s Got Talent singing star. Wayne Rooney, the footballer, and Richard Dawkins, the atheist, are considered “negative”.

“This is appalling,” the Rev Malcolm McMahon, the Roman Catholic Bishop of Nottingham, said. “You don’t invite someone to your country and then disrespect them in this way.”

Cardinal Renato Martino, former head of the Vatican’s Pontifical Council for Justice and Peace, said: “The British Government has invited the Pope as its guest and he should be treated with respect.

“To make a mockery of his beliefs and the beliefs of millions of Catholics, not just in Britain but across the world, is very offensive indeed.”

A Foreign Office spokesman said: “This is clearly a foolish document that does not in any way reflect UK Government or Foreign Office policy or views. Many of the ideas in the document are clearly ill-judged, naive and disrespectful.

“The text was not cleared or shown to ministers or senior officials before circulation. As soon as senior officials became aware of the document, it was withdrawn from circulation.

“The individual responsible has been transferred to other duties. He has been told orally and in writing that this was a serious error of judgment and has accepted this view.”

“The Foreign Office very much regrets this incident and is deeply sorry for the offence which it has caused. We strongly value the close and productive relationship between the UK Government and the Holy See and look forward to deepening this further with the visit of Pope Benedict to the UK later this year.”

It will be the first state visit of a pope to Britain. In 1982 Pope John Paul II toured for six days but that was paid for by the Church and was not a state visit.