Scott Woods, a model and actor, said yesterday he would have turned down the job had he known the full content of the advertisements. His comments follow the announcement by the Advertising Standards Authority that it was investigating complaints about the campaign.
Mr Woods, 42, of Hackney, east London, said: "I knew the image was going to be used in a Conservative Party "New Labour, New Danger" campaign, but they were only using my eyes and I had no idea they were going to superimpose it on a picture of Tony Blair.
"I'm unhappy about that and I think I would have turned the job down. It's all part of the dirty tricks campaign and I don't approve of that or being used in it."
Mr Woods, who appeared in Ken Russell's Treasure Island on Channel 4, and is about to play a serial killer in a new British film, The Lighthouse, admits to a certain resemblance to Boris Karloff and says he was chosen because of his menacing eyes.
"During the shoot I was told to look as sinister as possible, and they put blue contact lenses on me to make me look even more of a serial killer." The photograph was later coloured to give its a satanic look.
The actor, who was chosen from a list of models on the books of the Ugly Enterprises model agency, admits he is a Blair supporter but confesses he used to vote for Margaret Thatcher. "I think Tony Blair is trying to change things and I admire him for that."
Although open to the charge of self-publicity in coming forward, Mr Woods, who only took up acting a year ago and is thought to have been paid around pounds 200 for the work, did not tell his agent or model agency of yesterday's informal press conference. His motive, he said, was fear of exposure by a newspaper that was on his trail.
His comments yesterday touched a chord with a number of Conservative politicians who feel unhappy about the nature of such an attack on Mr Blair. The demonology aspect has been criticised by a leading churchman, and Mr Major himself is reported to be unhappy with the campaign.
A Central Office spokeswoman insisted that Mr Woods had "known from the start" how the photograph would be used, and said while there were no further plans to use them again, it had "not been ruled out".
Steve Hilton, of M&C Saatchi, which devised the campaign, said that at the time that Mr Woods did the photographs and a related video there were no plans to use the Blair newspaper advertisements, which were a response to Clare Short's interview in the New Statesman in which she spoke of dark forces behind the Labour leader.