Three quarters of so-called child asylum seekers in made to undergo medical tests to prove their age in Denmark have been found to be adults.

The Danish Immigration Service (DIS) suspected 800 migrants were lying about their age and asked the University of Copenhagen's Department of Forensic Medicine to run checks on them.

And having carried out tests involving x-rays of their teeth and bones, it was revealed 600 of the refugees involved were actually adults.

A group of migrants off an incoming train escorted by Swedish police as they gather on the platform at the Swedish end of the bridge between Sweden and Denmark in Malmo, Sweden

In Denmark, unaccompanied child migrants have the rights to a number of privileges under asylum law including bringing their parents to the country.

But Intergration Minister Inger Støjberg said the number of suspected age cheats is a good thing, and proof the Danish system is working.

'The Danish Immigration Service makes a major effort to expose those who are cheating and is also working on how it can happen even faster,' she told Jyllands-Posten.

Eva Singer, head of asylum at the Danish Refugee Council warned the tests might not be 100 percent accurate.

'There are many of these young people who don't know precisely how old they are because it is not something that is registered in their home countries in the same way as it is in Denmark,' she told Jyllands-Posten.

The DIS said it does not automatically dismiss paperwork from countries such as Afghanistan, and if a migrant's documentation says they are 17 and their tests suggest they are 18 or 19, the age would be registered as 17.

It is not an isolated problem in Denmark.

Almost 5,000 refugee ‘children’ who have come to Britain in the past decade have been found to be adults.

Home Office figures revealed in October show there have been 11,121 disputes over the ages of child asylum seekers in that period, with 4,828 – almost 45 per cent – found to be over 18.

Their treatment as ‘children’ would have left councils and local taxpayers facing a care bill of tens of millions of pounds a year.

Despite the concerns, the Home Office is advising its staff to only challenge the age of a ‘child’ migrant if they look ‘at least 25-years-old’, it emerged.

The issue was magnified by the demolition of the Calais Jungle migrant camp in which supposed child asylum seekers appeared far older than 18.