A controversy has erupted in Austria over a public arts project depicting Queen Elizabeth II, George W Bush and Jacques Chirac apparently having sex.
The posters were part of a series of 150 different images being flashed to motorists via billboards across Vienna.
The sex poster, and one of a woman lying naked on a bed, except for a pair of knickers bearing the EU flag, have been condemned as pornographic.
The scandal comes days before Austria takes over the EU presidency.
Chancellor Wolfgang Schuessel said he could not order removal of the posters, as it was an "independent artistic project".
Artists from across the European Union had contributed images on a range of subjects to the display, part of the 25Peaces art project which has received around 1m euros (£680,000) from the government.
The image by Spanish artist Carlos Aires, showing the naked threesome wearing rubber masks of the Queen and two presidents, has caused the most controversy.
But he is reported to claim it shows the "most recent changes in Europe and the resulting spatial constructions".
Organisers of the project, which celebrates 60 years of Austria's republic and 10 years of its membership of the EU, say the posters reflect the "different social, historical and political developments in Europe".
Other images in the series include a woman with a flower planted in her mouth, pink baby-grows full of packets of food and a businessman lying on top of a pile of crushed cars.
An EU-themed image, unlikely to go down well in Brussels, shows a scaffold made up of the words Equal Consuming Habits and Ideal Market, with EU flag forming the hangman's noose.
Georg Springer, organiser of the 25Peaces project, rejected the complaints of pornography.
He told Austrian ORF radio: "Nobody would describe [the painter] Egon Schiele as a pornographer".
But he said some of the posters would be taken down in the coming days.
Leader of Austria's right-wing Freedom Party (FPO) Heinz-Christian Strache described the Aires posters as "group sex fantasies".
Leader of Austria's Social Democrats (SPO) Norbert Darabos said he was not against artistic freedom but objected to the fact that the project had received 1m euros of federal funding.
Salzburg regional leader Gabi Burgstaller said the pictures were "not good for Europe" and were demeaning to women, adding: "One should avoid such things."
Other schemes in the 25Peaces project have included planting a vegetable garden on Heldenplatz - the square where Adolf Hitler announced Germany's annexation of Austria.