Christian Brueckner, the prime suspect in the disappearance of Madeleine McCann, managed to evade his round-the-clock surveillance when he got into a fight last month, officials have admitted.

The convicted rapist and paedophile, 49, was arrested alongside an unnamed British man after a clash in the northern German city of Kiel on April 20.

It prompted emergency talks among authorities in the state of Schleswig-Holstein, and opposition politicians demanded answers over how it could have happened. 

He has been fitted with an electronic ankle tag and is supposed to be under 24-hour surveillance by police, at significant cost to the German taxpayer.

His arrest came as it emerged that the Metropolitan Police has been making efforts to have Brueckner extradited to the UK, so that he could face trial in this country over the 2007 disappearance of Madeleine from Praia da Luz, Portugal, in 2007.

Now, German Interior Minister Magdalena Finke has admitted the episode showed that the surveillance operation around Brueckner failed.

She confirmed that he had given police officers the slip that day, the Mirror reports, despite a rolling operation to keep an eye on him since his release from prison in September last year.

He has been living in fenced-off container accommodation under strict monitoring conditions.

But police revealed he managed to stray around 200 metres away before entering a private property and becoming embroiled in a scrap.

A source close to Brueckner told the Mirror at the time: 'He got attacked by a British person. The guy appeared in front of him together with two other people and a big dog. 

'He yelled at Brueckner and hit him in the face twice and that's it and then the police came and arrested him. Brueckner called the police. He was injured.'

Both men were arrested on suspicion of 'mutual assault', and the police investigation is ongoing.

Finke has since insisted authorities were taking public fears 'very seriously' and claimed intense extra security measures had now been introduced.

Police have also reported that Brueckner has been making deliberate efforts to evade their surveillance, such as by cycling through narrow paths and side routes where their cars cannot follow. 

Brueckner returned to Kiel in March after serving a seven-year sentence for the brutal rape of an elderly American woman in Portugal in 2005.

Prosecutors had hoped to build a case against him in relation to Madeleine before his release, but were unable to gather sufficient evidence.

Since then, he has been in hiding and living rough, with locals hounding him out from various locations he has moved to to try and start a new life. 

He was ordered to wear an ankle tag so police could monitor his movements, but in November, a court ruled that it should not forbid him from travelling abroad as this was 'unconstitutional'.

Scotland Yard officers from Operation Grange - the unit set up to investigate Madeleine's disappearance - have contacted him to ask for his cooperation, but he has always refused to speak.

Speaking exclusively to the Daily Mail about the suggestion he might be extradited to the UK, a source close to Brueckner's legal team said earlier this month: 'We have been here many times before, and nothing has ever happened; we are sure this attempt will go the same way.

'If the UK authorities have any evidence and if they are so sure of it, why don't they share with the Germans so that they can look at it and press their own charges.

'German law forbids German citizens from being extradited to another country; they can only be put on trial in Germany, so the chances of this happening are non-existent.'

Meanwhile, another source close to Brueckner said: 'He has seen the news and is aware of it. He's completely unfazed by it. As far as he is concerned, they have had years to bring a case against him and have failed.

'He's very confident this won't be going anywhere soon, but then again, he has always been an arrogant and self-assured man.'

In letters sent to the Daily Mail, Brueckner always denied any involvement in the disappearance, insisting he was being made a scapegoat by German authorities. 

There is a large amount of circumstantial evidence linking Brueckner to the case - his mobile phone pinged close to the apartment where the three-year-old Madeleine disappeared from.

He has previous convictions for child abuse, and crucially, his name was given to both the German and British police by an informer in 2008.

They told detectives that Brueckner had told them a year after Madeleine vanished that she 'didn't scream' when she was taken.