A sex fiend who speaks English and wears a surgical mask is understood to be the kidnapper Portuguese police now fear may have snatched Madeleine McCann.

Detectives are now following this lead after they discovered that a man reportedly known to local police carried out nearly 30 attacks within a 40-mile radius of the holiday apartment in Praia da Luz from which Madeleine vanished 12 years ago Friday.

A judicial source is reported to have confirmed the unnamed man was definitely in Portugal at the time the British 3-year-old disappeared.

The insider also alleged the man was known to local cops and had previously been investigated on suspicion of involvement in pedophile cases.

He allegedly crept into Algarve properties rented by families, and many victims were British. In one case, a 7-year-old girl from the UK reportedly woke to find the pervert lying next to her in bed wearing a medical mask.

Portuguese cops are believed to be working on a tip from Scotland Yard about an alleged foreign pedophile.

Madeleine’s parents, Kate and Gerry McCann, are kept updated of any significant new development in the Metropolitan Police investigation, aided by their foreign counterparts. However, their spokesperson, Clarence Mitchell, declined to discuss the latest claim.

“We will not be commenting whatsoever on operational details in either Britain or Portugal,” Mitchell said. “We are not in a position to talk about it.”

But a friend of the McCanns is skeptical.

“It is just odd that news of this possible new lead has come out of the anniversary of Madeleine’s disappearance and we’re wondering if it could have been made up,” the friend said.

Investigators Anthony Summers and his wife, Robbyn Swan, who penned a book about the case and narrated the Netflix documentary “The Disappearance of Madeleine McCann,” said the masked intruder was one of at least 12 suspects police are probing.

“From what the little girls told their parents afterward, the man had come into the room wearing a sort of medical mask. He had a funny smell,” Summers said.

Swan said the holiday company that operated the Ocean Club resort where the McCanns were staying had refused to comment on whether they knew of these sexual assaults.

She said the Foreign and Commonwealth Office had declined to comment on why British vacationers had not been warned.

“Would they have left their children alone had they known there was a sexual predator about?” Swan said of the McCann case in the documentary.

Kate and Gerry McCann have already slammed the new Netflix documentary, saying it “won’t help” the search for their daughter.

Known to police

The family also believe the controversial new film could “fuel conspiracy theorists,” their spokesman said earlier.

A Metropolitan Police spokesperson said: “We have no response to this — we will not be giving a running commentary of an ongoing investigation.”

The new suspect’s nationality was not revealed in current reports.

News website Expresso claimed: “The PJ (Policia Judiciaria) is following a tip received from Scotland Yard and sent recently to Portugal relating to the Madeleine McCann case, Expresso has learned from a judicial source.

“According to the source, it relates to a complaint made about a foreigner who was in Portugal in May 2007, when the English girl disappeared from a tourist complex in Praia da Luz.

“The suspect is no stranger to the Portuguese police. At the time the PJ investigated him on suspicion of being involved in cases of pedophilia but in light of the information coming from London, the investigators are looking into this case in more detail.”

The source told the website: “This is a line of investigation that is still open. Like others.”

The national criminal investigation police agency of Portugal is already said to have spoken to witnesses who could help in connection with the new lead.

Asked Friday to comment on the latest reports in Portugal, including a report about Portuguese police having a “new suspect” and “new lead,” Portugal’s Attorney General’s Office repeated an answer it gave last month to a question about whether Scotland Yard had formally requested more help.

“Regarding these facts, as is public knowledge, an inquiry in the Portimao section of the Faro DIAP Public Prosecutors Office is ongoing. It is under investigation,” a spokesman said.

The news coincides with the 12th anniversary of Madeleine’s disappearance as the youngster’s parents vowed to carry on looking for their daughter “for as long as it takes.”