A child protection expert believes the man heading the Portuguese inquiry into the disappearance of Madeleine McCann has reached a crucial stage in the investigation.

Former police detective Mark Williams-Thomas said: "It's now time to make a decision about the line of inquiry which focuses on Kate and Gerry McCann.

"It's time to either make the case against them or release them from suspect status and put forward an alternative case."

Williams-Thomas, who has run major pedophile inquiries in Britain, is confident the new head of the investigation, Paulo Rebelo, has been through all the evidence and will now be looking at the possibilities.

He said: "There is now a new focus, a new team, and the new man heading the investigation has been in position for about three weeks.

"He's proactive and seems to be doing all the right things. He should have been involved from the start."

The Portuguese police's handling of the original investigation into Madeleine's disappearance six months ago has been widely criticized.

There were concerns that detectives did not secure the crime scene for long enough to gather adequate forensic material. The Portuguese were also criticized for failing to make a public appeal for witnesses.

Portuguese law constrains what information police can release, but Williams-Thomas hopes the law will be reviewed in the light of the Madeleine case.

In the meantime, the child protection consultant is encouraged by the way the investigation is now being handled.

Police have spent hours carrying out a re-enactment of the events on the night the little girl went missing.

He said: "This sort of reconstruction enables officers to throw about theories, discuss evidence and witness statements and pool information.

"They'll have been asking questions like: Is it possible the child could have opened the window; could the child have opened the door; could the door have been forced open from outside?

"Then they can eliminate any theories on the grounds of what's likely or unlikely.

"This is the way I would expect an investigation to be carried out. It's a positive new focus."