"I've always been a great fan of Muhammad Ali and his philosophy," says Reg Keys. "Whenever he got into the ring with Sonny Liston or George Foreman, nobody gave him a chance. But he always believed that he could win. And, when it really mattered, he did."

These are words that may well give Tony Blair a chill. For Keys intends to stand against the prime minister in his Sedgefield constituency in the general election, which is likely to be held on May 5. And Keys isn't just the run-of-the-mill, third-rate Tory candidate who usually contests safe Labour seats like Sedgefield; rather, he is someone who believes he has the singular moral authority to defeat Blair at the polls for taking Britain to war in Iraq.

For several weeks now, a group of Westminster MPs, along with the musician and record producer - and former Blairite - Brian Eno, have been looking for an independent candidate with sufficient clout to topple Blair from his safe seat in County Durham. Their aim was to find someone akin to Martin Bell, the former BBC reporter who, as an independent candidate, ousted the disgraced Conservative MP for Tatton, Neil Hamilton, in 1997.

In Keys, a 52-year-old retired ambulance training manager from the West Midlands, they believe they have found their man. "Unlike Martin Bell, I don't wear a white suit and I'm not used to the media. I've got a Midlands accent and I'm an introvert," says Keys. "I'm not exactly what you'd expect of a politician, but I do know that I can embarrass Tony Blair."

The reason he believes this is that Keys is a bereaved father who has entered the political process not out of personal ambition but to honour the memory of his dead son. Lance Corporal Tom Keys was a British military policeman killed by a 500-strong mob of Iraqis in the volatile Shia city of al Majarr al Kabir in June 2003. Keys believes that his son went to Iraq trusting the false prospectus for war that Blair set before the House of Commons.

"I want to hold Tony Blair to account for his deceit," he says. "I remember the last time I saw Tom, at New Street Station in Birmingham in February 2003, when he marched off down that platform with his chest puffed out, proud to be off to do his duty for Britain. He believed what he was told... But Blair lied to him, and to all those other 84 soldiers who came home in coffins after fighting in a war that was illegal and immoral."

Does he really believe that he can topple the prime minister in a constituency where, historically, they don't so much count Labour votes as weigh them? "I have got to believe that I can. Whenever I have any doubts about what I am doing I just think about Tom. I just think of when I dressed Tom and brushed his hair when his remains were returned to me, his body riddled with bullet holes.

"I suppose the Paxman question is 'Why are you standing in Sedgefield - you're not from there at all?' That's true. But it's also true that Tony Blair isn't a local. He was educated in Scotland and lives in London. Yes, he has a house in the constituency, but the only time he comes to Sedgefield is when he's with his posh friends and he wants a photo opportunity. I am as local as he is."

Keys longs for a face-to-face debate with Blair about the war. "I would love that challenge. If he believes his actions were just and that no ministerial codes were broken, then he has nothing to fear. I don't believe, though, that he has nothing to hide. He knew that the intelligence that was used to justify war was shaky."

Keys had originally intended to stand against Defence Secretary Geoff Hoon in his Ashfield constituency. "Then I met this hostage negotiator called Felicity Arbuthnot who worked with [the murdered aid worker] Margaret Hassan, and she said, why not stand against Blair? She put me in touch with Brian Eno and some of his friends, and I realised that it would be a good idea."
Who's bankrolling your campaign? "Well, not Brian Eno. He's given us his moral support and let us use his studio in London, but he isn't backing us financially.

So far we're just surviving on minor donations of £100 and £200, but hopefully we'll get some bigger donations as the campaign goes on. I'm struggling to pay the £50-a-night bed and breakfast bills." He says that a local pub has offered him the free use of a back room as campaign headquarters. Not the Dun Cow, the Sedgefield pub where Blair has entertained several world leaders in recent years? "No, the pub which offered us the room doesn't want its name disclosed."

The question now is whether Keys and his supporters can encourage other political parties that had intended to contest Sedgefield to stand down so that he can get a straight fight with Blair. "The Tory candidate has already stood down. I don't know for certain whether they're going to put anyone else up in their place, but I think it's unlikely," says Keys. "I'm not sure whether the Lib Dems are going to stand, but I am hoping that we can negotiate with them. Already an anti-war independent candidate has decided to throw his weight - both moral and financial - behind me."

He also hopes to convince another potential independent candidate, the former spy David Shayler, to stand down. "We're trying to have a negotiation with him, but it may be that he has a book he wants to promote."

Yesterday, Keys arrived in Sedgefield to test the water for his campaign. It would take a 22% swing for him to defeat Blair, who, in 2001, was elected with a majority of 17,713. What struck him about the town? "It was how run down the school playgrounds looked, and it just made me think of the £5bn that was wasted on the war, how far money like that would have gone in making places for our children to play properly."

Isn't Sedgefield a constituency from which many British soldiers come and so would have strong views about your campaign? "That's right. What amazed me, though, is that some people I have spoken to need to be educated. Some seemed to think that Saddam was involved in 9/11 and that there were weapons of mass destruction."

He says that one of the first people he met was a soldier on leave. "He was just a young lad, like my son Tom was. And he really disagreed with what I was doing. He said: 'I signed on the dotted line, so no one can really complain when I'm killed on active service.'

"I can understand him saying that. But what happened with Tom was that he was killed in the middle of a war we shouldn't have been fighting, and killed in a manner that showed the army had underestimated the danger of the situation into which they were sending those young men. Tom had, when he was 18, been part of a mission with the SAS to rescue a regiment. Had he been killed in that action, no argument. Or had he been killed by a weapon of mass destruction while on active service in Iraq, no argument. But he wasn't."

Keys argues that his son died as part of an army blunder. "Three weeks before Tom was killed, the army had what it called a 'scale down'. They took away his morphine, grenades and all his ammunition except just 50 rounds. It also took away the radio masts, so that all they had were vehicle-mounted, year-old Clansman radios, which were notoriously unreliable. They tried to get hold of satellite phones but for some reason they were refused.

"In that condition he was sent to this volatile Shia city where he and his section found a violent mob of 500 heading for the police station. They didn't have a chance. The Iraqi police fled, but Tom and the rest of them fought until they had no more ammunition. Then they were killed by a mob in a ritualistic fashion, which is common there." All six of the British Red Caps were murdered.

"There were no medals or honour for them. There was no letter from Tony Blair. Instead, he managed to find time to write a letter of condolence for Ozzy Osbourne when he fell off his quad bike. But not to my son, who was shot 31 times. I can't help but think angrily about that, and about Tom's beautiful green eyes. He was four days short of his 21st birthday."

He does have happier memories. "Before Tom went to Iraq, everything was rosy. We were a family of four. Two sons. I had retired, as had my wife, who was a hospital ward manager. We had moved to a barn conversion in Bala in north Wales. All that life has been ruined for us."

Is it difficult to be a political candidate in these circumstances, when you are still clearly grieving? "Yes it is. It's worse for my wife. We're both very fragile, but it is worse for her. My son is buried in a beautiful grave at Llanaber near Barmouth in Wales. A very picturesque spot overlooking the sea. But my wife can't bring herself to go there. She can't quite bring herself to see his name on the grave. It's too final.

"I feel, though, that I have a responsibility to Tom. I keep going back to the words of a widow of a man who died on the Kursk [the Soviet nuclear submarine whose crew perished in 2000 in an underwater disaster after its reactor melted down]. She said: 'If you betray your country you are a traitor and you will go to prison. But if your country betrays you, what can you do?' I think I have an answer to that: we can use our vote to get rid of those people who betrayed my son and other men like him. That's what I want the people of Sedgefield to do."

The Iraq Solidarity Campaign is supporting Reg Keys in his stand against the British Prime Minister, Tony Blair.

A speacial ISC meeting is going to be held on Wednesday 23rd March, where Reg will be coming to Manchester and addressing an ISC public Meeting.