A convicted British paedophile has insisted he has never seen missing Madeleine McCann other than in posters and on television.

Raymond Hewlett, whom detectives working for the McCann family have tried and failed to interview, said: “I’d take a lie detector test.

“I’ll take any test you like. The only time I’ve seen Madeleine McCann is on missing posters. And I saw her on TV in a bar once. But I’ve never seen her in real life.”

Final attempts by the detectives to interview Hewlett failed on Wednesday.

Retired RUC detective Dave Edgar and another former British officer, Arthur Cowley, flew to Germany the day before hoping to speak to Hewlett, who is said to have been staying an hour’s drive from the McCanns’ Portuguese holiday flat when the little girl vanished.

But negotiations between the private investigators and Hewlett’s German lawyer broke down, leading Mr Edgar, who has been employed by Madeleine’s parents Kate and Gerry McCann to look for their daughter, to say he was “very disappointed” with the lawyer’s behaviour.

He said: “I have been attempting to speak with Raymond Hewlett to eliminate him from our investigation into the disappearance of Madeleine McCann.

“He is not a suspect, but I was keen to interview him because of his failing health.”

The detective said he had been told that the paedophile could only manage a 60-minute interview when to quiz him properly would take five hours.

Hewlett, 64, a former soldier who previously lived in Blackpool and Telford, has been treated for throat cancer in Aachen.

He was jailed several times in the UK for sexually assaulting young girls, including an attack in 1978 where he put a gun to his victim’s back.

West Yorkshire Police has confirmed its officers are investigating Hewlett in connection with an indecent assault in 1975.

The Sunday Mirror said Hewlett had been discharged from hospital by doctors who said there was nothing more they could do for him, and he is wasting away on the fourth floor of a tower block.

He said: “It’s obvious why they’re interested in me. But they can all think what they like. I didn’t kill the McCann girl. It’s the truth and it’s never going to change.”

The newspaper says that Hewlett admits he was in the Algarve at the time of Madeleine’s disappearance and he looks like a pock marked suspect seen lurking around the apartment.

He also refuses to give an alibi for the night when Madeleine vanished.

“There is a person who can say where I was that day, but why should I bring them into this? I’ve done nothing wrong,” he said.

Madeleine was nearly four when she went missing from Praia da Luz in the Algarve on May 3, 2007, while her parents dined with friends nearby. There has been no trace of her since.