A controversial DNA test used in the failed Omagh bomb case is the key to finding Madeleine McCann’s kidnapper, Ulster investigator Dave Edgar has claimed.

But the former RUC detective sergeant’s team will never be able to use it as Portuguese authorities will not give him access to forensic information.

Speaking exclusively to Sunday Life at the HQ of his Alpha Investigations Group in Cheshire, the ex-cop leading the search for Maddie believes that DNA tests, which can establish a profile from just a few cells, could help solve the mystery.

Edgar said he tries to maintain “a decent relationship” with Algarve cops but has blasted them for contaminating the scene of her disappearance.

He claimed if Low Copy Number (LCN) DNA testing had been carried out at the Ocean Club resort in Praia da Luz, where Maddie vanished from two years and four months ago, it is “highly likely” her abductor would have been nailed.

LCN DNA is a highly sensitive forensic procedure which magnifies potential evidence that is unidentifiable by traditional DNA testing.

It can obtain a perpetrator’s profile from only a few cells as small as a millionth the size of a grain of salt. Some argue its magnification method leaves evidence open to distortion.

Doubts were raised when south Armagh electrician Sean Hoey was cleared of charges connected to the Omagh bombing in a case which focused on LCN DNA.

But Dave has seen it work before. His team used it in 2007 to snare killer Stephen Mottram, who stabbed love-rival Andrew Batterton to death in a jealous rage.

Dave said: “It’s an amazingly powerful tool, so it’s a real shame we will never get to use it with Maddie.”

Prosecutors in the Omagh case claimed that LCN analysis had shown links between the bomb timers used in the attack and Hoey.

But the judge rejected the use of the technique because it was not yet seen to be at a sufficiently scientific level to be considered evidence and Hoey was cleared of a total of 58 charges, including 29 murders.

A UK-wide suspension of the technique after the Omagh case collapsed was lifted in January of last year and detectives are now free to use it again.

The PSNI has championed Low Copy Number DNA analysis, pointing out that it helped catch Trevor Hamilton, the serial offender who brutally murdered Strabane pensioner Attracta Harron in December 2003.

LCN DNA was also crucial to the conviction fireman Gordon Graham for the 2000 murder of

Lisburn man Paul Gault, husband of Graham’s Fire Service lover Lesley, a mum of triplets.

Graham battered his love rival to death with a hockey stick and tried to the make the killing look like work of a burglar.

But Graham’s attempt to commit the ‘perfect crime’ was undone by traces of his sweat found on the handle of sports bag at the Gault's Audley Park home.

Graham, who has always denied the murder, was ordered to serve a minimum 18 years behind bars by the judge who branded him “brutal and merciless” killer.