The photograph of Mr Blair making a regrettable hand gesture was taken when he was a student at Oxford University in the mid-Seventies.

It has been reproduced in newspapers dozens of times since it first appeared – only without the gesture.

After the original version was unveiled on Newsnight last night, it was reported that the picture had never been seen in its full glory because it had always been cropped to avoid embarrassing Mr Blair.

In fact, it turns out his hand signal was removed by computer manipulation on the insistence of the clergyman who supplied the photograph and with the agreement of the news agency which distributed it to newspapers.

The picture first surfaced in 1994. Labour leader John Smith had just died and papers were casting around to work out who would succeed him.

The front-runner was Mr Blair and the Bristol agency, South West News, found the picture in the possession of Father Nicholas Lowton, 52, a contemporary at Oxford. It showed Mr Blair, in blazer and straw boater, with fellow members of the Archery Club, a university dining club, in 1975.

Paul Walters, the agency’s picture editor, said: “We arranged to copy the picture. Father Nicholas said, ‘ Obviously make sure you don’t copy that element of the picture.’

“We said, ‘fine’ and that is what we have always done. It has been a secret that everyone has known for many years and it was only a matter of time before it all came out.”

Father Nicholas told Newsnight: “I suppose the BBC lawyers would be a bit worried if I was to suggest he was drunk in that photo. On the other hand, it’s probably more defamatory to say he was sober.”

He described Mr Blair as a student who was “averagely naughty, without being wicked”. He added: “It was all fairly innocent. Tony always knew how to keep his nose clean.”