Gordon Brown's distinctive facial features have proved a real headache for an artist who has spent six years searching for his lookalike.
Mr Brown has proved difficult to emulate
Alison Jackson, known for celebrity mock-up photos and Double Take series, blamed his "huge bovine features" for her thwarted quest.
She said she had never had such trouble finding a lookalike, and had been dreading Mr Brown becoming PM.
"It's the size of the head maybe... nobody comes close," she told the BBC.
Ms Jackson has made a career of photographing doubles of famous people in compromising positions, and making shows such as BBC 2's Double Take and Channel 4's Blaired Vision.
Among her faked photos are Mr Brown's predecessor Tony Blair letting President Bush win a game of tennis and David Beckham wearing his wife's underwear.
But she has admitted defeat on finding a convincing double for Mr Brown and has advertised open casting sessions, held in conjunction with Esquire magazine, which will publish the photos when he is found.
Asked what the problem was, Ms Jackson said: "I've been trying to work it out. Is it his Celtic features? I'm going to Scotland to try and find someone who might look like him - what is it?
"He's got this huge jaw and most people don't have a jaw that kind of size. It's not even the details of his mouth drop or the eye thing - it's something to do with the whole head shape," she said.
"It's just been very very difficult to find the face that fits... I just don't know, but nobody comes close."
While Ms Jackson might find his features unusual - New Woman Magazine last year voted Mr Brown among the world's 100 sexiest men, alongside the likes of Bond star Daniel Craig and fellow actor Johnny Depp.
In an interview with a woman's magazine in 2006, Mr Brown said his wife Sarah thought George Clooney should play him, in a film of his life.