Gallery stamped on!

You would hardly lick the back of them, stick them on a letter and pop them in the post - after all, these pictures measure 22 by 24 inches and feature the Queen wearing a gasmask.

Nevertheless they have sparked an extraordinary row between the Royal Mail and a London gallery.

Tom Tom, in New Compton Street, is being threatened with legal action for attempting to sell the three joke images, entitled Stamps Of Mass Destruction.

The Royal Mail says the prints infringe its copyright and must be handed over or destroyed.

The gallery, which was founded 10 years ago and has sold works by artists including Andy Warhol, is refusing - claiming it is the victim of "bullying tactics".

The prints were created last year in the run up to the war in Iraq by James Cauty, half of the notorious techno group KLF. An edition of 150 copies was put on sale through Brighton gallery artrepublic until The Royal Mail successfully demanded their withdrawal.

Gary Mitchell, owner of Tom Tom, put his three copies - the artist's first proofs - on sale in May for £10,000. A Royal Mail investigator soon came calling, demanding they be taken down, and a solicitor's letter - delivered by hand - followed the next day.

Mr Mitchell said: "We have offered to withdraw them from sale but we don't want to give them up."

A Royal Mail spokesperson said: "The matter is with our legal team. Obviously we hope to sort it out amicably."