The mother of Madeleine McCann insisted that her daughter may still be held captive in an abductor's home, as her family recruit private detectives to collect information about sightings.

Kate McCann wept uncontrollably as she spoke about her hope for Madeleine's return in the first television interview since she was made an official suspect in her daughter's disappearance.

Mrs McCann said: “I think she is possibly being held by someone in their house but I don't know. As Madeleine's mummy I feel in my heart that she is there.

“I don't know how anyone could harm anyone as beautiful as Madeleine. I don't mean her appearance. I mean as a beautiful person.”

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Mrs McCann and her husband, Gerry, have insisted that their daughter was abducted by a stranger from their holiday apartment in Praia da Luz in the Algarve on May 3.

She broke down during an interview with a Spanish television programme to be broadcast tonight after saying: “I feel sad and I feel lonely and our life is not as happy without Madeleine. I feel anxious she is not with us.”

The McCanns gave the interview on the advice of private investigators, based in Spain, who have been hired by the couple. The investigators have set up a confidential 24-hour phone line to take calls on the case.

The family had been warned previously that they could be prosecuted for speaking about the case under Portuguese laws of judicial secrecy. However, their lawyers approved the interview on condition that they did not discuss evidence.

The couple spoke to the Spanish channel Antena 3 because they wanted to promote the helpline across the Iberian peninsula and in North Africa. They are confident that the helpline does not break Portuguese laws banning outside involvement in criminal cases.

Mrs McCann, 39, said: “It is six months and I strongly believe Madeleine is out there and we have to do everything we can. Somebody knows something. It is not about us. It is about Madeleine. We have not even seen her since she was four. She needs our help. She needs her family.”

Mrs McCann, a GP, said that her two-year-old twins Sean and Amelie still asked about when their elder sister would be returning to their home in Rothley Leicestershire.

“They are not upset and they are not distressed but they are very much aware she is not there,” she said. “The hardest thing for me is when they [the twins] say, ‘When is Madeleine coming back home?' and we have to say, ‘We don't know but everyone is looking for her'.”

Her husband, a consultant cardiologist, said: “The thing is, we want people to come forward with any information whatsoever that can help to find her and we want them to be aware of this [telephone] number.”

The couple are suspected by Portuguese detectives of killing their daughter accidentally, six days before of her fourth birthday, and then disposing of her body illegally before inventing a claim that she had been abducted.

Three Portuguese detectives are expected to arrive in Britain this week to reinterview at least four of the seven British friends who were on holiday with the McCanns at the Ocean Club resort. The detectives are expected to be present during interviews by Leicestershire police officers.

Reports in Portugal claim that the detectives have found samples that indicate Madeleine died in the flat and that her corpse was carried in the boot of a car hired by her parents 25 days after she was reported missing.

Mr McCann said: “We have not been charged with anything. Investigations are continuing. We are certainly not scared. There is no evidence DNA tests will show anything other than us being completely innocent.”

The information hotline is being operated by the Barcelona office of Metodo 3, one of Spain's best known firms of private investigators, which has 20 detectives.

Clarence Mitchell, spokesman for Mr and Mrs McCann, insisted that the new helpline would not side-step the Portuguese police investigation into Madeleine's disappearance.

“This, in effect, is going to be a complementary structure,” he said. “One where our own investigators are able to chase things up very quickly, follow up any potential leads, and I would stress that any credible information that comes in to the phoneline is immediately shared with the respective police forces, either in Spain, Portugal, or North Africa, depending on what the information is.

“This is not a sign of losing faith. We want this to be a collaborative exercise with the police.”

The information line numbers is 902 300213 within Spain; 0034 902 300213 from outside the country.

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