An Afghan who claimed to be just 12 is revealed to be in his twenties after assaulting his British foster father.

The Afghan teen, who had arrived in Britain illegally via Calais, was actually registered as a child but after a dental examination found that he had rotting wisdom teeth, a dentist suggested he was more likely to be an adult.

The revelation came after another British carer also reported that she was sexually assaulted by an alleged teen she was looking after.

The Afghan teen, who had arrived in Britain illegally, was registered as 16 but after a dental assessment it was revealed he more like to be between the age of 18 and 21. Pictured, thousands of refugees arrive in Europe

A petition signed by Benedict Cumberbatch (pictured left) and Richard Branson has urged the government to take in more refugees from war-torn countries such as Syria

MPs have now called for new rules regarding age assessment for immigrants despite a petition backed by celebrities such as actor Benedict Cumberbatch and Virgin tycoon Richard Branson saying that refugee children should be reunited with their British relatives.

If they enter Britain as children, asylum seekers are immediately put into the care of social services which often leaves youngsters separated from their parents for long periods of time.

Conservative MP for Monmouth David Davies spoke to MailOnline about an attack on one of his female constituents who was looking after the '12-year-old' immigrant.

The Afghan was taken in by the Welsh foster family but refused to live by their rules and would skip school and disappear for long periods.

He told social services that he wished to move to Bristol but when told he would have to live with a foster family, he became angry and attacked his foster father.

It was after the fracas that the man's phone was confiscated and indecent images of children and visits to Jihadi websites were found.

Mr Davies said: 'They did a dental check on him and discovered that his wisdom teeth were rotting.

'The dentist said he had to be in at least his 20s but the Home Office strike people down to 16 if they don't know what their age is for certain, so he was listed as 16.'

Mr Davies said that Britain was being fooled by fraudster immigrants who knew how to play our system.

David Davies MP (pictured) claimed that one asylum seeker was caught looking at indecent images of children

He said: 'These people come over here and get preferential treatment by claiming they're 12 and no one wants to call them out.

'We've seen how bad things can get with other incidents in Europe, like what happened to that poor girl murdered in Sweden. It's becoming common place.'

Mr Davies added: 'They're encouraged to lie because if they say they are 12 they are allowed to stay in the country for six years until they face being kicked out.

'But when their six years is over and they're being forced to leave they just turn around and say it's a breach of their human rights. It's all a complete ruse.'

Government guidelines state that an individual should be treated as an adult if two separate officials deem them to look 'significantly' over 18 and if there is 'clear and credible documentary evidence'.

The comments from Mr Davies come just weeks after two shocking pictures emerged of migrant 'children' in Sweden.

The first photo was of Iraqi Saad Alsaud, who despite looking like a man in his twenties, is reported to have been just 14.

Saad Alsaud is reported to have been the fastest 14-year-old in Sweden, dwarfing younger boys and girls in a running event

The other shows a Somalian named Youssaf Khaliif Nuur who claims he is 15 though he is 6ft tall and, according to one unconfirmed source, shaves his beard and moustache.

He appeared in a Swedish court on January 28, accused of stabbing 22-year-old aid worker Alexandra Mezher to death at a young migrants' hostel.

The extraordinary pictures of the two men were published in the Swedish press to show how enthusiastically the politically correct nation welcomes in orphaned young migrants.

The growing scandal over the issue was highlighted with the murder of Miss Mezher in the Gothenburg hostel, where her mother says residents lie about their age to get preferential asylum treatment.

She was stabbed after trying to break up a fight between two youths.

Youssaf Khaliif Nuur was charged with her killing and when he arrived in court the Somalian was said to tower over his translator.

Youssaf Khaliif Nuur who claims he is 15 though he is 6ft tall and, according to one unconfirmed source, shaves his beard and moustache

For her part, psychology graduate Miss Mezher had warned her mother that she was caring for 'big powerful guys' aged up to 24, in a shelter designed for children aged 14 to 17.

The Swedish experience would seem to lend support to the stance of David Cameron who has rejected calls to throw open Britain's doors to migrant children arriving alone in Europe.

Last month the Prime Minister promised to 'resettle' genuine orphans from Middle East refugee camps and some stranded in Greece and Italy.

In Britain, Kent County Council, being closest to the Channel, already receives vast numbers of child migrants, many smuggled by traffickers into the UK from the squalid French coast camps at Calais and Dunkirk.

Last year, as the migration crisis blew up, the numbers of children arriving in the Garden of England surged.