Civil servant Steven Mulvain, 23, had sent the memo with a covering letter urging that it "should not be shared externally" because it included "even the most far-fetched of ideas" for Pope Benedict XVI's planned visit to the UK, The Daily Telegraph reports.
These included the Pope opening an abortion clinic, the launch of 'Benedict'-branded condoms, the sponsoring of a network of AIDS clinics and the announcement of a training course for bishops accused of child abuse.
An official statement read: "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."
Vatican spokesman Rev Federico Lombardi responded: "They supplied all the explanations, and there is nothing to add."
Scientist Richard Dawkins recently caused controversy when he suggested that the Pope should be arrested and tried in a civil court in relation to the ongoing clerical sexual abuse scandal affecting the Vatican.