An Post has been forced to defer the issuing of a Irish Citizen Army stamp because of a dispute over an image used on the stamp.

The 60c stamp was due to be issued today to commemorate the Irish Citizen Army.

It featured a man believed to be Jack White, a former British Army Captain who volunteered to train the Irish Citizen Army.

However, it emerged yesterday that the man featured may not actually be Capt White.

An Post said: "This image, which was researched and verified, has been widely used over the years in academic journals and other publications.

"However, following advance publicity for the stamp yesterday, a number of historians have disputed the veracity of the image saying the man depicted is not Jack White."

It said it was delaying the issuing of the stamp until the issue has been resolved.

It was confirmed this evening that the Cabinet signed-off on the design of the stamp and that 136,000 had been printed at a cost of €4,000.