A family of Afghan asylum seekers deported to Germany after seeking sanctuary in a British mosque are "desperate" to return to the UK following a High Court ruling that ministers acted illegally, supporters said today.

Farid Ahmadi, 33, his wife Fariba, 25, and their two young children, aged five and three, were last month flown back to Germany, where they had first claimed asylum. They travelled on a specially-chartered military jet at a cost to the taxpayer of an estimated £30,000.

But today Mr Justice Scott Baker, sitting in London, ruled: "As a result of an unlawful act, this family were removed from this country when they should not have been."

The decision provoked an angry response from Mr Blunkett, who warned it would be exploited by "every illegal immigrant and failed asylum seeker". Mr Justice Scott Baker indicated he was inclined to order the family's return so their human rights case could be heard.

But Philip Havers QC, for the Home Secretary, suggested they should stay in Germany and conduct a challenge by video link, with the Home Office giving them all the assistance they needed to present their case.

Campaigner Paul Rowlands, who is currently in Germany with the Ahmadis, said the family were keenly awaiting tomorrow's developments and wanted to return to Lye, near Stourbridge in the West Midlands, where they lived before their deportation.

"Farid and Fariba are very happy from what they have heard so far from the court, but don't want to say too much at this stage," said Mr Rowlands, who with his partner Soraya Walton befriended the family when they came to the West Midlands.

"The family are desperate to get back home and to get the children back to school. We are here to support them all the way."

A spokeswoman for Mr Blunkett said: "It is the Home Secretary's view that this will create such a precedent that every illegal immigrant and failed asylum seeker will cite psychological damages to frustrate the proper operation of asylum laws.

"Before today, this case had already been looked at by six separate judges, all of whom decided that the Home Office had acted entirely within UK and international law."

The Home Secretary was "disappointed" with the judgment and the Government would seek leave to appeal, she added. Keith Best, chief executive of the Immigration Advisory Service, said that the decision could have a huge impact on Mr Blunkett's plans to reform the asylum system.

The politician's Nationality, Immigration and Asylum Bill proposes sending some unsuccessful asylum applicants to another country and forcing them to conduct their appeals from there.

"This should be a warning to the Government over their changes to the appeals process," said Mr Best. "We believe this system would be impractical. It could also lead to injustice."

The judge ruled the family should have been allowed to remain while they challenged their removal on human rights grounds that the mother and children's mental health would suffer if they were sent back to Germany.

The Home Secretary had been wrong to rule, in the light of medical evidence of their mental sufferings, that they had "no arguable case" and their challenge was "manifestly unfounded".

The family, who came to Britain in June 2001 after complaining of their treatment in Germany, had sought sanctuary in a mosque at Lye.

The parents were later forcibly removed in a raid by police and immigration officers after the Home Secretary ruled it was the German authorities who had responsibility for determining their asylum claim.

During a one-day hearing yesterday, David Pannick QC, appearing for the family, accused Mr Blunkett and the Home Office immigration authorities of "breaking the rules" in the rush to get the family back to Germany.

The judge accepted Mr Pannick's arguments and said: "In my judgment the Secretary of State could not lawfully conclude that the matters raised under Article 8 of the European Convention on Human Rights were manifestly unfounded on the basis of the medical evidence before him."

During the hearing family lawyers supplied evidence, questioned by the Home Office, that since returning to Germany the family was in a "disturbed and distressed" state, and medical reports referred to the "traumatised behaviour" of the children and the "suicidal" state of the mother.

Medical reports had suggested that deporting Fariba and her daughter Hadia, five, and son Seera, three, would cause them "considerable mental harm". The Ahmadis - not their real name _ fled Afghanistan in 2000, claiming they had been tortured and persecuted by the Taleban.

They spent seven months in Germany but claim to have suffered racism and bigotry there.

Philip Havers QC, appearing for the Home Secretary, said there had been a "misunderstanding" over what would happen to the Ahmadi family on being eturned to Germany.

Ian Taylor, the Home Office case worker, had written a letter considered by Mr Justice Evans when he refused to grant an order to prevent deportation, saying the Ahmadis could expect to live in the community as settled residents.

Mr Havers said there were errors in the letter, but Mr Taylor had not intended to create any false impression and still maintained the Ahmadis had access to all necessary services and facilities in Germany, even though they were required to live in a residential centre.

The case was adjourned until tomorrow morning for further argument on whether the Ahmadis should return to the UK