Kate McCann has had herself tested for drugs to counter accusations that she was on medication when her daughter Madeleine vanished.

Mrs McCann agreed to the tests to refute claims that she was mentally unstable and taking anti-depressants around the time of the child's disappearance in Portugal in May.

One line of inquiry reportedly pursued by Portuguese police was that she had killed Madeleine because she was struggling to cope.

Results of toxicology tests on Mrs McCann's hair, taken in September, show no evidence of drugs in her body over the past eight months, according to her lawyer, Edward Smethurst.

He said: 'There were various stories circulating that Kate might somehow be unstable and might be depressed and whatever, but the tests demonstrated that the kind of drugs she might be on did not show up.'

The tests form part of a dossier of evidence compiled by the McCanns and their advisers, which they claim demolishes the police case against them.

DNA checks on a car hired by the couple in Portugal and research on the use of cadaver dogs in police investigations further bolster their defence case, their lawyers say.

Kate and her husband Gerry, from Rothley in Leicestershire, deny any involvement in their daughter's disappearance from their holiday apartment in Praia da Luz.

Mr Smethurst said: 'I am taking this case on free of charge, on a pro bono basis. I am here for no other reason than to see that justice is done.

'I have had access to the full evidence in this case. The fact that I am here continuing with the case is that I am completely convinced of the innocence of Kate and Gerry.'