Maddie 'was overdosed on sleeping pills'

Leading French newspaper France Soir said sources had made the claim following toxicological tests on a liquid found in the boot of her parents' hired car.

It is the latest in a string of leaks' from Portuguese police, who say they now want to re-interview Madeleine's mother so they can ask her more than 40 questions she previously refused to answer.

Kate McCann remained silent when detectives initially put the questions to her in the presence of her lawyer, sources said.

Police also want fresh interviews with some of the friends on holiday in Portugal with her and her husband Gerry when Madeleine went missing.

Mrs McCann's private diary documents her struggles to look after her "hysterical" children and reveals details about the night Madeleine went missing, it was reported.

The diary is reportedly among a number of personal items prosecutors want from the young girl's parents.

Mrs McCann was frequently seen writing her journal in private moments after Madeleine went missing from the family's holiday apartment in the Algarve resort of Praia da Luz on May 3.

Detectives appear to be working on a theory Mrs McCann killed Madeleine by accident and covered up the death by claiming she was abducted.

Mr McCann's alleged role is not clear, but sources say police believe he might have been an accessory to the killing.

But Mr McCann said these were "ludicrous accusations".

Meanwhile, social workers visited Madeleine's parents at their home in Rothley, Leicestershire, yesterday to discuss the welfare of their other two children.

The McCanns invited the officials for talks about two-year-old twins Sean and Amelie in the light of their being named as suspects in their eldest daughter's disappearance.

It is not known what was discussed at the meeting or what, if anything, was decided from it.

Mr McCann's brother, John, said: "They will co-operate with anyone who has the family's best interests at heart."