Mum-of-five Nikki Fetzko says the Home Office has written to 22-year-old James Ailmore informing him he will be re-arrested at the prison gates and put on a plane.
Ailmore is due for release on July 7 – having served half of a 16-month sentence for affray and theft.
Miss Fetzko, of Wartnaby Road, Ab Kettleby, said: "James was born in Germany because his dad was in the Army and was stationed in Fallingbostel at the time.
"We lived there for a couple of years and then came back to Melton where James has lived ever since. He isn't German. I can't understand why the Home Office wants to send him there.
"We can't find his birth certificate but I am almost 100 per cent sure it says he is a British national. James has been a bit of a nuisance and I think that's why they are doing it.
"But he's only really been in trouble for things like theft, he's never murdered or attempted to murder anybody like some of the illegal immigrants who are running around free and have not been deported.
"There are terrorists who have hijacked planes and they get given asylum."
Miss Fetzko is additionally concerned about her son because he became a father for the first time on Sunday.
"James has been looking forward to the birth, but now it looks like he won't get to see his son.
"He's in a terrible state, I don't know what they are trying to do to the lad.
"James was expecting to come home but the Home Office has notified the prison governor to say he will have to leave the country. On his release he will be put on a plane and sent to Germany.
"I can't believe it. He's got a military birth certificate. If he was German national then he would have been called to do National Service in the German Army.
"He's got no family out there and doesn't know anybody in the country, what's he supposed to do? I haven't been contacted by the Home Office and I'm his mother."
Miss Fetzko is seeking legal assistance in a bid to make sure her son comes home.
A spokesman for the Home Office refused to comment on individual cases, but said: "We would never seek to deport anyone who is a British citizen. When someone is subject to removal proceedings they need to provide evidence to prove they are a British citizen."
tara.rippin@meltontoday.co.uk