PORTUGUESE detectives yesterday accused the mother of missing Madeleine McCann of killing her daughter.

Kate McCann, 39, fears she could be charged over the girl's death after being named as an "arguida", or formal suspect, in the case.

She returned to the family's rented house in the Algarve village of Praia da Luz last night after being quizzed by police for five hours.

Meanwhile, Madeleine's aunt, Philomena McCann, last night claimed that Portuguese detectives had offered Mrs McCann a deal if she confessed to accidentally killing Madeleine.

In a interview with ITV News, she said: "They tried to get her to confess to having accidentally killed Madeleine by offering her a deal through her lawyer - 'if you say you killed Madeleine by accident and then hid her and disposed of the body, then we can guarantee you a two-year jail sentence or even less'."

In a day of dramatic developments, Madeleine's father, Gerry, 39, was also summoned back to the headquarters of the Policia Judiciaria - Portugal's CID - in the town of Portimao for further questioning.

Mr McCann arrived at the police station at about 3.35pm, a few minutes before his wife left looking drained and shell-shocked.

He began his interview as a witness, but police could also make him an arguido if they need to ask him potentially incriminating questions.

Portuguese detectives appear to be working on the theory that Mrs McCann killed her daughter by accident and covered up the death by claiming she was abducted.

Test results from the Forensic Science Service in Birmingham, received in recent days, have apparently boosted this hypothesis.

Mr McCann's alleged role is not clear, but sources said police believe he was an accessory.

Mrs McCann underwent 11 hours of questioning on Thursday, during the course of which detectives suggested that traces of Madeleine's DNA were found in the family's hire car, a silver Renault Scenic that they are still using.

She is understood to have told them angrily there was "no way" this could be the case because they did not lease the vehicle until 25 days after her daughter disappeared.

After returning to the police station yesterday morning, Mrs McCann was formally made an arguida and detectives put 22 key questions to her.

A family spokesman said: "It was clearly suggested to her that she had accidentally been responsible for Madeleine's death."

Mrs McCann, who, like her husband, strenuously insists she is innocent, was said to be "shocked and frustrated" by yesterday's developments.

The spokesman said: "She is upset but bearing up, and frustrated that all this attention has been paid to this, rather than trying to find Madeleine.

"She is confident in that she obviously thinks the whole suggestion is ridiculous."

Hundreds of locals and holidaymakers joined a huge crowd of journalists waiting outside Portimao police station throughout the day. Mrs McCann's arrival was greeted with whistles and jeers from Portuguese onlookers, although one British holidaymaker shouted: "We believe you Kate."

Family and friends immediately came to Mrs McCann's support, dismissing any suggestion she could have been involved in Madeleine's disappearance on May 3 as ridiculous.

Susan Healey, Mrs McCann's mother, described the situation as "ludicrous".

Before attending the police station, Mr McCann said he and his wife would fight the moves to implicate her "all the way".

Writing on his blog, on the www.findmadeleine.com website, he said: "Anyone who knows anything about May 3 knows that Kate is completely innocent."

His brother, John McCann, labelled the moves by Portuguese police as "crazy", saying the idea that blood found in a hire car could link Mrs McCann to Madeleine's death made no sense.

He also said there was growing frustration with the Portuguese police's methods and called for them to get their investigation back on track.

"There's a degree of almost anger, it's more frustration. We just want them to get on with the real focus," he said.

"My wee niece is missing and it's not Gerry and Kate that are involved in this. Let's get back to the real reason. What's happened to that?"

The seven friends on holiday with the McCanns when Madeleine disappeared also released a statement saying they were "totally appalled" at Portuguese police allegations.

They said: "She is innocent - we know this because we are her friends, we were with her on the night, and we witnessed first hand the unimaginable grief Kate and Gerry suffered and continue to suffer."

But asked if the family would be shocked if Mrs McCann was to be charged, another friend said: "Nothing now would surprise us."

It is 128 days since Madeleine went missing from her family's holiday apartment in Praia da Luz, while her parents dined with friends nearby.

Until now, there has been only one arguido in the case - Anglo-Portuguese expatriate Robert Murat - but he is widely expected to be formally ruled out of the inquiry shortly.

Under Portuguese law, an arguido has legal protection that is not extended to a witness, including the right to remain silent during questioning and the right to legal representation.