Tests on Kate and Gerry McCann's other two children support their insistence that they never sedated their missing daughter Madeleine, it was reported today.
Analysis of hair samples from their two-year-old twins Sean and Amelie found no evidence of sedatives, according to London's Evening Standard.
This would add strength to the couple's vehement denial of allegations they had given their three children sleeping pills on the night Madeleine vanished from the family's holiday apartment in Praia da Luz, southern Portugal, on May 3.
The McCanns' official spokesman, Clarence Mitchell, refused to confirm or deny the report.
He said: "We will not comment on any of the legal aspects of this case.
"Our lawyers are looking at all of the issues raised by the case very closely indeed.
"Kate and Gerry have already made it quite clear that they have never used sedatives on their children."
Mr and Mrs McCann have faced a series of allegations since detectives named them as formal suspects in Madeleine's disappearance on September 7.
They strongly deny any involvement, and have said they are considering legal action against media organisations that suggest they drugged their children.
The toxicology tests on the twins' hair form part of a dossier of evidence compiled by the McCanns' lawyers to help clear their names, the Evening Standard reported.
Their team at London law firm Kingsley Napley also has evidence to disprove allegations Mr McCann is not Madeleine's biological father, the paper said.
A source close to the couple told the Evening Standard: "It would be logical for tests to be carried out on the twins to show they have never been given sedatives.
"It would be right to say those tests show no evidence of sedatives in their systems.
"It backs up Kate and Gerry's claims they have never sedated the children and explains why they are so certain they can prove the allegation is just another police smear."
Meanwhile, Prime Minister Gordon Brown has spoken about the Madeleine investigation with his Portuguese counterpart at an EU summit in Lisbon.
His spokesman said today Mr Brown had a "brief discussion" about the case with Portuguese prime minister Jose Socrates.
The spokesman added: "They both agreed what matters was there should be the closest possible co-operation between the Portuguese and British police."
Mr Brown has in the past had telephone contact with Madeleine's parents and has received regular briefings on the case since the young girl's disappearance on May 3.
Direct contact ended when the couple were named as suspects because of the sensitive nature of their legal status, according to reports.