Investigators probing the disappearance of Madeleine McCann in Portugal have identified a British pedophile as a possible suspect, a spokesman for Madeleine's parents told British media.

Raymond Hewlett, 64, was reportedly living less than an hour away from the resort of Praia da Luz when 3-year-old Madeleine disappeared in May 2007, The Sun reported.

Hewlett closely resembled an artist's impression of a man seen near the McCanns' holiday apartment.

He was originally given an alibi by a 15-year-old girl at the time of Madeleine's disappearance, but has since "made bizarre comments about the case to his friends and family," according to The Sun.

He allegedly told a British couple vacationing in Praia da Luz that "gypsies" had offered him money to sell one of his own six children.

Hewlett was jailed for a year after raping a 12-year-old girl in 1972, then got four years for attacking another girl at gunpoint in 1978.

He later served a six-year sentence for a 1988 sex attack on a girl of 14 and is currently in Germany being treated for cancer.

Kate and Gerry McCann's spokesman confirmed that Hewlett was "of interest" to British investigators working for the couple.

"We are aware of Raymond Hewlett and the claims that have been made about him in some newspapers," spokesman Clarence Mitchell said. "The investigators searching for Madeleine are currently looking into the circumstances surrounding these claims."

Madeleine's parents earlier this week announced they are going to sue former Portuguese Police Chief Goncalo Amaral for defamation.

Kate and Gerry McCann are taking the action over comments made by the man who previously led the inquiry into Madeleine's disappearance.

In a statement, they said: "We — together with our three children Madeleine, Sean and Amelie — are taking this legal action against Goncalo Amaral over his entirely unfounded and grossly defamatory claims - made in all types of media, both within Portugal and beyond — that Madeleine is not only dead, but that we, her parents, were somehow involved in concealing her body."

The McCanns said they are taking action because his claims that Madeleine is dead are hampering the search for their daughter.

They want a gagging order to prevent further publication of Amaral's "deeply offensive" book "The Truth of the Lie."

The McCanns also want to block broadcast of his TV documentary and publication of his "disgraceful thesis" that they were involved in their daughter's disappearance.

Click to read more on this story from The Sun.