Two-thirds of failed asylum seekers who came to Britain more than a decade ago are still in the country, Sky News has learned.
There are also people who have committed multiple crimes who the Home Office has failed to deport.
One man who was originally born in Malaysia but moved to Britain as a baby told us he was reporting in to the Home Office to fight deportation after minor drugs offences.
He said: “I don”t think the Home Office policy is effective at all. Even with a case like mine.
“I feel like I”ve got a good chance (of winning) so that”s why I”m stringing it out.”
The Home Office has said the number of foreign criminals being deported from the UK is increasing.
But it is not just criminals the authorities are struggling to deal with.
Examining 11 years of data, Sky News has found the percentage of people who have failed to leave the country after being refused asylum is consistently high.
Of more than 24,000 asylum applicants in 2004 who were refused permission to stay in the UK, 65% are officially still in the country.
In 2010 – which saw the highest number of people leaving – there were nearly 11,000 failed asylum seekers of which 52% are still here.
And of the 8,634 failed applicants in 2014, 62% remain in Britain.
Rajasooryer Ramanatha has been in Britain for 17 years.
He was allowed to stay in the country after admitting drink driving.
The 39-year-old then continued to offend with a total of 19 convictions over a 10 year period, including sexual assault and battery.
Mr Ramantha is from Sri Lanka where he says he was tortured and that affected his mental health.
He claims his life would be in danger if he returned.
A year ago he was given a deportation order by the Home Office, but since then he has managed to stay in the UK illegally.
Despite this Britain is still paying for his psychiatric care.
He said: “I couldn”t control myself. Sometimes my head”s blown up you know like past memories, like dreams and nightmares.”
He said he thought Britain had been generous to him and had been well treated by the Home Office.
“They have treated me well but I spoil myself because of my medical condition you know. I”m just asking for another chance,” he added.
One Somali man who did not want to be identified told us he had been in Britain for more than 20 years.
He was convicted of grievous bodily harm, but after serving his sentence he says he was kept in prison because the Home Office could not decide what to do with him. He is now out on bail.
Even he cannot work out why he has not been deported.
He said: “Obviously they did put in the deportation order … I did not understand why it did not go ahead.
“I was in prison for almost six months over my time but now I”m out.
“It doesn”t make sense to me.
“You”re telling me on paper that I”m going to abscond but you”re giving me bail.”
A Home Office spokesperson said: “Foreign nationals who abuse our hospitality by committing crimes in the UK should be in no doubt of our determination to deport them.
“And, if they refuse to leave voluntarily, we will also enforce the removal of those who have claimed asylum but been found not to be in need of our protection.
“Last-minute legal challenges have been one of the major causes of delayed removals, which is why the Government legislated to make it harder for people to lodge spurious appeals.
“Deported offenders can now launch an appeal from their own country, rather than clogging up the British justice system.”