Paedophile Raymond Hewlett has insisted he knows nothing about Madeleine McCann's disappearance.

The convicted sex offender, whom detectives working for the McCann family have tried and failed to interview, told a newspaper: "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 detectives employed by Madeleine's parents Kate and Gerry McCann to interview Hewlett failed on Wednesday.

Retired UK policemen Dave Edgar and 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.

Hewlett, 64, an ex-soldier who previously lived in Blackpool and Telford, has been treated for throat cancer in Aachen. He has reportedly been discharged from hospital by doctors who said there was nothing more they could do for him.

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.

Hewlett 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 pockmarked suspect seen lurking around the apartment in Praia da Luz. He also refuses to give an alibi for the night of May 3, 2007, when Madeleine went missing.

© Independent Television News Limited 2009. All rights reserved.