The lawyer of Robert Murat, the first suspect in the case of missing Madeleine McCann, has launched an astonishing personal attack on her parents and the detective agency they have hired to find their daughter.

Francisco Pagarete, who has acted for Mr Murat since he was made an arguido on May 14, gave an interview to a Portuguese newspaper in which he branded Kate and Gerry McCann “hypocrites” and said they should be “cursed” for leaving their children alone.

"The McCanns deserve to be cursed...for leaving their children unprotected,” he told Portuguese daily 24 Horas commenting on the fact that the McCanns had left Madeleine and her siblings, twins Sean and Amelie, 2, alone in the apartment while they dined with friends in a nearby Tapas restaurant on the night of May 3.

"I'm just sorry that there are people out there ready to support a couple who abandoned their three children."

"Meanwhile my client, his mother and his girlfriend, who have done nothing wrong, are seeing their name dragged through the mud on a daily basis."

His remarks follow a series of claims that detectives at Metodo 3, the Spanish agency brought in by the McCanns in September, have new information allegedly linking both Mr Murat and his German girlfriend Michaela Walczuch, both 34, to the abduction of Madeleine McCann.

They are said to be following up two alleged sightings of a woman identified by witnesses as Ms Walczuch with a child matching Madeleine's description.

And it has also been reported that they had spoken to a nanny at the resort who in December had allegedly seen a man “identical” to Mr Murat attempting to break into apartment 5A - the apartment later rented by the McCanns at the Ocean Club in Praia da Luz.

But Mr Murat, who shares a villa with his 71-year-old mother less than 100 yards from the McCanns apartment, denies any wrongdoing and has called for an end to the “smear campaign” he believes has been launched against him from the McCann camp.

Mr Murat's lawyer went on to label the Barcelona based detective agency “mercenaries” and said that his client was considering suing the company for making a series of “unsubstantiated slurs”.

"Metodo 3 are mercenaries" he said.

"The detectives are persecuting my client and his girlfriend who as a result no longer have a private life,” said Mr Pagarete.

"This is simply unacceptable in a democratic state,” he said and issued the warning: “Leave my client alone.”

The Portuguese authorities have said they are aware of the investigations being carried out by Metodo 3 and have warned them that they could breach Portuguese law if they “interfere” in the case.

Clarence Mitchell, the official spokesman for the McCanns has said the couple continue to put their faith in Metodo 3.

"We have every confidence in M3's abilities to investigate Madeleine's disappearance and at whatever stage, where it is relevant, they are happy to share information with the Portuguese Police,” he said.

"Everything M3 does on this case is within the law.”