Detectives have been given an extra £154,000 to continue the decade-long search for Madeleine McCann as they are hunting a 'person of significance'.

The Home Office confirmed it will fund work to chase up a 'critical' lead in Scotland Yard's inquiry.

The figure brings the total spent in 2017-18 on Operation Grange to £309,000 and the overall cost to around £11.5million.

Senior detectives expect the investigation into her disappearance will now continue until at least March.

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They said the final element of their probe, which remains shrouded in secrecy, has proved much more 'complex' than first expected.

Madeleine had been left alone sleeping with her younger twin siblings while her parents were dining in a nearby tapas restaurant. Photo / Supplied
Madeleine had been left alone sleeping with her younger twin siblings while her parents were dining in a nearby tapas restaurant. Photo / Supplied

The size of the award will raise hopes that the force is closing in on identifying whoever abducted the three-year-old in May 2007 - but it also raises questions about what the money will be spent on, as only four officers remain on the case.

Her parents Kate and Gerry insist they must continue as there is "absolutely nothing" to suggest their daughter has been harmed, the MailOnline reported.

Not one piece of forensic evidence linked to the little girl has been found since she vanished from her family's Praia da Luz holiday apartment.

And despite trawling through thousands of tip-offs and potential sightings, police have not confirmed that a single one was her. Last year, then-commissioner of the Metropolitan Police Sir Bernard Hogan-Howe said the squad was expecting to mothball their work within months.

But on the tenth anniversary of her disappearance police described the remaining lead as "critical" and of "great interest".

Her parents Kate and Gerry insist they must continue as there is 'absolutely nothing' to suggest their daughter has been harmed. Photo / Getty
Her parents Kate and Gerry insist they must continue as there is 'absolutely nothing' to suggest their daughter has been harmed. Photo / Getty

It is understood police chiefs have a working theory on what happened to Madeleine but may be unable to reveal it publicly because it implicates an individual or individuals.

The Portuguese investigation of Madeleine's disappearance was criticised by the British authorities as being not fit for purpose. Scotland Yard began an investigative review into the disappearance in 2011, on the orders of then-Prime Minister David Cameron.

However, The Sunday Times understands Met detectives have been relying on Portuguese transcripts of key interviews with British witnesses, rather than conducting their own.

Operation Grange has conducted no formal witness interviews with Gerry or Kate McCann or the seven friends they dined with on the night Madeleine disappeared.

Speaking a few weeks ago, a spokesman for the family said the McCanns remain "extremely thankful" to police for requesting extra funding.

Three-year-old Madeleine vanished from a holiday apartment in Portugal's Praia da Luz in May 2007. Photo / Getty
Three-year-old Madeleine vanished from a holiday apartment in Portugal's Praia da Luz in May 2007. Photo / Getty

Their representative, Clarence Mitchell, said: "They are very encouraged there remains work to be done that requires them seeking an extra budget.

"They are grateful to all those officers who are still working on the case and are actively looking for Madeleine.

"They appreciate everything the police have done and are doing everything to get a resolution after all this time."

Scotland Yard has insisted it will not reduce the small team left on the case any further as the "inquiry has not reached a conclusion".