Efforts to clear the parents of Madeleine McCann of any suspicion were stepped up today amid expectations of fresh police questioning.

As Portuguese detectives reportedly flew in to the UK with a list of fresh questions for Kate and Gerry McCann, friends of the couple gave the first outline of their possible defence.

Sources close to the family insist much of the police's evidence - including the collection of Madeleine's DNA from the family's hire car in Praia da Luz - can be easily explained.

The car was used to transport much of the youngster's items when the family moved to a new apartment some time after her disappearance from their original holiday let in Praia Da Luz on May 3.

Items said to have been carried include nappies worn by her twin brother and sister Sean and Amelia, who have similar DNA it was reported today. Madeleine's own sandals are also believed to have been transported in the car - potentially allowing DNA from sweat to be transferred.

A source said the vehicle had also been used by a number of people, including several family members, before it was examined.

Three Portuguese officers are reported to have arrived in Britain ahead of a fresh interrogation of the McCanns.

The couple, both 39, returned to their home in Rothley, Leicestershire, last week after spending four months in Portugal awaiting developments.

It was reported today that the officers want Leicestershire Police to put questions to the McCanns, who have been declared official suspects in the case, although they deny any involvement in her disappearance or death.

"The Portuguese police will not be asking the McCanns questions directly, but will be providing a list of questions that the Leicestershire Police should ask," one source closer to the investigation was reported to have said.

But a spokeswoman for the McCanns said: "To date, we have had no contact from them, no request, nothing like that... if they are on their way, they have in no way let the family or the legal team know."

The couple told reporters they will probably return to Portugal one day.

"There are lots of reasons - spiritual, emotional and social - to return to Portugal quite apart from the investigation," Mrs McCann said.

"Equally we may wish to go back to discuss things with our lawyers and discuss the search for Madeleine with the police, regardless of what is going on at present.

"We will be going back as and when we wish. We are not seeking to run."