Pictures of the Queen wearing a gas mask which are on display in an art gallery in Brighton have caused a row with the Royal Mail.
The pictures are on display in artrepublic in the North Lanes
Three images representing first, second and third class stamps are on display at artrepublic in the North Lanes.
They were created by former pop star James Cauty, who was in the group KLF, and are supposed to reflect his stance on the war with Iraq.
But now the Royal Mail has said using the Queen's head is a breach of its copyright.
We have had one or two objections and thousands of compliments
Lawrence Alkin, gallery owner
Gallery owner Lawrence Alkin said: "Artrepublic has always been about demystifying art and bringing it to a mass audience.
"Nothing is original, it is through thousands of years of evolution of ideas - artistic and scientific - that has brought our culture to where it is today. So I am quite amazed.
"It has had a fantastic reception. We have had one or two objections and thousands of compliments.
"We have never sold a limited edition as fast as this one."
The images, which have been created through the Giclée printing technique, have been on display at the gallery since May.
A spokesman for the Royal Mail said: "We do take any breach of copyright very seriously especially in relation to the Queen's image.
"We produce over three billion of these stamps every year and the images belong to the Royal Mail.
"It is still too early to say what action we will take. We hope this will be sorted out amicably."
The Royal Mail has given the artrepublic until Friday to take the images down.
But Mr Alkin has said he is seeking legal advice on the issue.