It also warned experts from Sprakab went beyond their remit, commenting on issues such as applicants' knowledge of their country of origin or demeanour.

The ruling has been welcomed by immigration lawyers and campaigners, who claim it is a positive step in ensuring asylum seekers get a fair hearing.

Jennifer Todd, an immigration solicitor with Latta Law, said: "I think this judgment is a positive development for practitioners and asylum seekers.

It was worrying when you looked at the format of the reports, and these people who were said to be language experts would go on to comment on the person's knowledge of the country, which had nothing to do with linguistics.

This judgment has now pulled back from that and it states that the reports shouldn't be given so much weight in a case. It will hopefully mean asylum tribunals will get the chance to really look and listen to other evidence and not just rely on the Sprakab reports."

But she warned it came too late in cases where asylum seekers have already been deported.

There will have been cases when people have been removed incorrectly," she said. "They use these reports a lot and, of course, the irony is that the applicants are sent back to where they claim to be from, rather than where the Home Office believes them to be from."

The Home Office last night insisted there would be no impact on other cases. But Ms Todd said: "This is a significant judgment which will have a wide impact on immigration cases.

"There will no doubt be numerous appeals arising from this, and also fresh applications."

Gary Christie, acting head of the Scottish Refugee Council, said: "We welcome today's ruling as it highlights just how essential it is to treat all claims for asylum fairly and individually. We hope this is a strong reminder to the Home Office that language analysis needs to be used with caution."

Another legal source involved in the Supreme Court case added: "This will have an impact on future cases, with tribunals entering into criticism of Sprakab until the review is complete and new guidance is issued. "But the major question is what it means for past cases. There could easily have been cases where applicants have been removed from the country wrongly based on these reports. Read more