A new picture of a possible suspect connected to the disappearance of Madeleine McCann is to be released by police, it has been claimed.

Sky News reported that British detectives investigating Madeleine's disappearance are to issue the "e-fit" in the next couple of days but Scotland Yard would neither confirm nor deny the claim.

In a statement, the Metropolitan Police said: "We are not prepared to discuss, comment or speculate on the content of the upcoming appeal in relation to the investigation into the disappearance of Madeleine McCann.

"This has been weeks in the planning and each element of the investigation must be set into the overall context of the appeal.

"We will be asking for help from the public in a number of countries, delivered through a series of public appeals.

"We will do nothing to jeopardise the effectiveness of these appeals and we have repeatedly stated that media speculation can be damaging to our efforts.

"The MPS will release the relevant material at the relevant time."

Madeleine disappeared from her family's holiday apartment in Praia da Luz in the Algarve on May 3 2007 as her parents dined at a nearby restaurant with friends.

British detectives launched a fresh investigation in July this year - two years into a review of the case - and a new BBC Crimewatch appeal on the case is to be aired on Monday.

The appeal will include a reconstruction of the "latest, most detailed understanding" of the events around the time Madeleine went missing.

Scotland Yard has revealed a vast log of mobile phone traffic could be the key to finding out what happened to the girl.

Madeleine's parents have said they remain "optimistic" of finding their daughter and will not accept she is dead until they are presented with clear evidence.

The Metropolitan Police now has a team of six Portuguese detectives based in Faro who are carrying out inquiries on its behalf.

The Portuguese investigation is officially closed but authorities there are backing the Scotland Yard inquiry and officers from both countries will work together in pursuing new leads.

Yesterday it emerged that Madeleine's mother Kate McCann has asked to give evidence at the libel trial of former Portuguese police chief Goncalo Amaral, over claims in his book The Truth of the Lie.

Her husband Gerry McCann is fighting to give evidence at the trial in Lisbon, and it was revealed that the couple's lawyer Isabel Duarte last week applied for Kate to step into the witness box as well.

The judge is yet to rule on the application, as well as one by Mr Amaral.

Last week Gerry's sister Trish Cameron told the court that the family's pain over Madeleine's disappearance was "multiplied 100 times" by the book.

She said the youngster's parents had been left in "purgatory" and the book and subsequent documentary had seen them "vilified" and "demonised".

The trial has previously heard how Mrs McCann had suicidal thoughts in the aftermath of the book's publication in 2008.

The McCanns say the former detective's claims in the book, including suggestions that they hid their daughter's body after she died in an accident and faked an abduction, damaged the hunt for Madeleine and exacerbated their anguish.

If successful they stand to gain around £1 million in damages.

Several e-fits of possible suspects have emerged since Madeleine's disappearance.

One, which became known as the "egg with hair", sparked ridicule because of its lack of facial features.

It was claimed that Portuguese detectives took the image around Praia da Luz in the days after Madeleine's disappearance.

Police refused to release the picture to the public, citing strict Portuguese laws covering investigations, but those who saw it were left baffled.

Praia da Luz shopkeeper Simon Russell said: ''They just showed me this outline which apparently gave me the impression that it had high cheekbones and a long face but other than that, no eyes, no nose, no mouth, so I call it an egg, it was an egg with hair.

''It didn't look like it had been drawn, it didn't look like a photograph, it looked like something that had been created maybe on a computer - but there were no features.

''It was completely different from anything I have seen in the newspapers - there were no features, there were no ears.''

In January 2008 the McCanns' team released an artist's impression of an olive-skinned man with straggly, collar-length hair and a distinctive drooping moustache based on a statement given by British holidaymaker Gail Cooper.

In July 2008 Portuguese authorities shelved their investigation into Madeleine's disappearance, and the next month thousands of pages from the official police files were released.

The documents included computer-generated e-fits of two suspicious men seen hanging around Praia da Luz before Madeleine went missing which were never made public by detectives.

It is believed that both men were investigated and discounted.