Kate and Gerry McCann may have to wait a year to discover whether they will be charged or cleared over the disappearance of their daughter Madeleine, they have been warned.

As they made an emotional return to their home in Rothley, Leicestershire, 130 days after the four-year-old went missing, Portuguese police made it clear the investigation was not over "by any means".

The couple now fear the "cloud of suspicion" which hangs over their heads after they were named as formal suspects in the case will divert attention away from the search for Madeleine and leave them increasingly isolated in their attempts to find her.

They are also said to be "terrified" that their two-year-old twins, Sean and Amelie, could be taken into care if they are charged with any crime.

The McCanns had always clung to the belief that they would eventually return home with Madeleine, but instead Mr McCann faced the cameras at East Midlands airport as part of a family of four, forced to deny he and his wife were to blame for their daughter's disappearance.

Struggling to maintain his composure, Mr McCann, 39, said: "Portuguese law prohibits us from commenting on the police investigation. Despite there being so much we wish to say we are unable to do so except to say this: we have played no part in the disappearance of our lovely daughter Madeleine."

The McCanns were both named as "arguidos", or formal suspects, on Friday after two days of police interviews during which Mrs McCann was offered a "deal" of a suspended prison sentence if she admitted to "accidentally" killing her daughter and told police where the body was.

The move is reported to have followed the discovery of traces of blood in a hire car used by the McCanns, but serious doubts have been raised about the value of the evidence, leading to speculation that Portuguese police are unlikely to bring charges unless more evidence comes to light.

In an interview which Mrs McCann gave hours before being declared a suspect, which was published on Sunday, she said: "They want me to lie - I'm being framed.

"They are basically saying, if I confess Madeleine had an accident, and that I panicked and hid the body in a bag for a month then got rid of it in a hire car, I'd get a two or three years' suspended sentence.

"I was even told: 'Think about it - Gerry would even be able to work again.' It is ridiculous."

A spokesman for the couple said they were willing to return to Portugal to answer further questions "at any time" and that they had "nothing to hide".

Explaining the decision to return home, Mr McCann said: "After very careful thought, we want the twins to live an ordinary life in their home country.

"While it is heartbreaking to return to the UK without Madeleine, it does not mean we are giving up our search for her. As parents, we cannot give up on our daughter until we know what has happened."

The couple had decided late on Saturday night to book themselves on to an EasyJet flight from Faro to East Midlands airport, which landed shortly after noon.

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They drove home to Rothley, where Madeleine's bedroom remains exactly as it was the day she excitedly left for the family holiday on April 28.

Although Mr McCann made a brief return to the house weeks after Madeleine's disappearance, it was the first time his 39-year-old wife had gone home.

A family friend said they had been reluctant to return home, as they are increasingly concerned that the investigation will grind to a halt without their continued presence in Portugal.

"The worst thing would be for the case to run down while this horrendous cloud of suspicion hangs over their heads," the friend said.

"There is a real concern that the Portuguese police now put this investigation in a dusty filing cabinet, never to be opened again."

Chief Insp Olegario Sousa, the police spokesman for the McCann case, insisted the investigation was "not over by any means".

He added: "The investigation will only end when we think the case file is complete and we hand our findings to the public prosecutor who then decides whether to drop the case or bring charges."

Sources close to the case said the process could take up to a year.

The McCanns had more bad news when they were told a request for the case to be reviewed by British police had been turned down.

Jacqui Smith, the Home Secretary, said she was satisfied with the way Portuguese police have conducted the investigation.