The picture, taken during a training exercise, shows one officer jokingly aiming a shotgun at a second as he stands on the bonnet of an armoured LandRover. Both men also carry Glock pistols which were believed to be loaded at the time.
Yesterday Greater Manchester Police (GMP) admitted that the officer's behaviour fell "well short" of expected professional standards.
The emergence of the image was also condemned by the family of a police officer tragically shot dead during a similar exercise with the same unit in 2008.
GMP firearms officer Pc Ian Terry was killed when a colleague "instinctively" fired at him from close range with a Remington 870 pump-action 12-bore shotgun. The specialist round, designed to burst car tyres, proved deadly.
A statement issued by lawyers for Pc Terry's family, Ralli solicitors, said: "Ian's family are extremely distressed at the sight of the image released today.
"It highlights that GMP, and in particular the tactical fire arms unit, haven't learnt anything from the circumstances surround the tragic death of Ian Terry.
"The family understand that the photograph was taken 18 months to two years after Ian's death, which would be at the same time as the inquest was being heard."
Yesterday, Greater Manchester Police revealed they had launched an investigation into the photograph after finding it on a computer during an "unrelated" raid on another officer's home in June last year.
It shows two specialist armed officers wearing full body armour posing for a picture believed to have been taken by an instructor of the elite unit.
Following the inquiry by GMP's Professional Standards branch, all three men were moved out of the Tactical Firearms Unit.
The unit, which is on call all year round, is based in east Manchester and trains officers as specialist marksman capable of dealing with armed robbery scenarios or terrorist alerts.
Referring to the picture, Deputy Chief Constable Ian Hopkins said yesterday: "Greater Manchester Police expects the highest professional standards from all officers and staff and, clearly, this falls well short.
"This matter was dealt with quickly as soon as it came to light in June 2011 and the three officers involved were removed from the firearms unit.
"Their conduct let themselves, their colleagues and the rest of the force down."
Pc Terry, a married father-of-two from Burnley, Lancashire, was shot dead during a training exercise with the Tactical Firearms Unit at an empty warehouse in Newton Heath, Manchester, in June 2008.
His inquest heard that there had been systematic failings with the planning and operation of the role-playing drill.
Earlier this month the Crown Prosecution Service announced that no one is to face criminal charges over the tragedy. But the Health and Safety Executive has said that it is to prosecute GMP over the incident. No court date has yet been set.
