The grandmother of missing Madeleine McCann believes the four-year-old was drugged by her abductor to stop her screaming out and raising the alarm.

Kate and Gerry spent a quiet day in Rothley, Leics

Eileen McCann, Gerry McCann’s mother, said it was the only way a stranger could have snatched her granddaughter as she lay sleeping in her parents’ rented apartment at the Ocean Club in the Algarve town of Praia da Luz on May 3.

Speaking on the 150th day since Madeleine went missing and ahead of a renewed publicity campaign aimed at finding her, the 69-year-old told the Belfast Telegraph the family were “going through hell” as the endless stream of police leaks about Gerry and Kate’s involvement in their daughter’s disappearance continued.

Mrs McCann, who lives in Scotland and runs a pub, said: “I really believe they (whoever took her) gave her a drug.

“There is no way they carried her out of there without her awakening.

“If she was taken when she was sleeping by somebody she did not know, she would have screamed the place down.”

The McCanns have denied claims in the Portuguese press that they themselves gave their children sedatives so they could go out to dinner with their friends.

It has been reported that police are working on a theory that Kate McCann killed her daughter accidentally, and the couple hid her body before eventually disposing of it.

But Mrs McCann dismissed claims that her granddaughter’s DNA was found in a Renault Scenic the McCanns hired weeks after Madeleine disappeared as “nonsense” and insisted that her son and daughter-in-law, both aged 39 and doctors, were innocent.

“Little Amelie is wearing Madeleine’s sandals and she is in and out of the car. Cuddly toys are in it. Madeleine’s toys are in it. Madeleine’s tops are in it that Amelie is wearing. It’s nonsense,” she said.

It also emerged today that the McCanns are considering suggestions by Scottish relatives that they take advice from psychics to find their daughter.

The couple, from Rothley in Leicestershire, have had more than 1,000 approaches from people claiming to be mediums and offering help but although any information deemed to be credible has been passed on to police, the McCanns have had no direct contact with any of them.

“They are desperate for help and even some family members are suggesting it as a possible route,” a friend said.

“It looks like one or two family members are saying why don’t you have a look at so and so.”

Next week, posters will be put up on billboards in Spain, Portugal and Morocco as part of a renewed campaign to raise awareness about Madeleine’s disappearance.

Although their status as official suspects means they cannot discuss details of the case or rebut some of the rumours circulating about it, Kate and Gerry McCann are also hoping to conduct a series of television interviews with Spanish and Portuguese networks.

“They are certainly looking at what they can do in line with the legal constraints and if that happens in time for the advertising campaign that would be great,” a source said.