Bernard Hogan-Howe, the Commissioner of the Metropolitan Police, has indicated that the investigation into the disappearance of Madeleine McCann may be wound down.

Portuguese police are refusing to reopen the inquiry Photo: PA

 Scotland Yard is to ask David Cameron whether the Government will continue to fund the inquiry into the missing child, who was last seen in her parents' holiday apartment in Praia da Luz, Portugal, in 2007.

The Met opened a new inquiry, Operation Grange, 15 months ago at the request of Mr Cameron. The Government has provided an 'open cheque' into the review of the case. The inquiry has 28 homicide detectives and seven civilian staff working full-time and is thought to have cost £2.5m so far.

Mr Hogan-Howe is asking for a new commitment on financing the investigation, in comments that suggest there may be a limit on how long the police are willing to spend on the case. Previously he has said there is no limit to the time and manpower available to the probe.

He said the police are sifting through a "large cache" of documents. Portuguese police are refusing to reopen the inquiry.

Mr Hogan Howe said: "We are still reviewing a lot of material. It is a significant amount of money and we have quite a lot of officers tied up in this. 

"There will be a point at which we and the Government will want to make a decision about what the likely outcome is.

"The Prime Minister agreed to fund this. We have not had any pressure to say you must stop spending more than x amount, we have received a lot of support. But by Christmas I would want a very clear view of what work is outstanding and what time line there is for that," the London Evening Standard quoted Mr Hogan-Howe as saying. 

This year Det Chief Insp Redwood, who is leading the inquiry, said he believed Madeleine had been abducted by a stranger and could be alive