A judge said the decision was flawed because the father of five, who can be identified only as BM, had not been given enough information to be able to instruct lawyers to challenge his exile.

But the judge said he would have upheld the move if the law had allowed him to rely on the secret evidence kept from BM.

BM, 36, is accused by the security services of being "a prominent member of a network of Islamist extremists".

He was forced, through a modification to a control order already restricting his movements, to move out of the east London area to a one-bedroom flat in Leicester.

The Government said the move was necessary to stop BM associating with his extremist contacts "with a view to engaging in terrorist-related activity" and there was a danger of him absconding.

BM's lawyers argued at the High Court in London that his continuing "internal exile", imposed in May, infringed his civil right to occupy his home.

Mr Justice Mitting has agreed and ruled the modification deprived BM "of a civil right for a significant period".

The judge said the Home Secretary had attempted to justify interfering with that right by arguing there was a risk of BM absconding and his removal from London was necessary to minimise that risk. But the Government had refused to disclose its secret reasons openly, and that meant the decision to make the modification had to be treated as flawed.

But the judge said there was "closed material" - evidence heard by him in secret - that would have led to him coming to a different decision if the law had allowed him to take it into account. The judge gave the Home Secretary seven days to revoke the order and return BM to his home. Government lawyers are considering whether to mount an urgent appeal.