Richard Ford, Home Correspondent

Thousands of highly skilled migrants who were faced with deportation can now stay in Britain, a court ruled yesterday. The ruling is a blow to the Government and its attempt to demonstrate to the public that it is taking a tough stance to meet concern over the extent of immigration.

Sir George Newman, a High Court judge, branded the new rules unfair and migrant groups claim that they could mean up to 44,000 people having to leave the country. The numbers are disputed by the Home Office, which says that only 1,370 applicants are affected.

Under the old rules migrants had to say they intended to make their main home in Britain and were allowed to stay for a year initially. They could then apply for a two-year extension and a further three years before seeking permanent settlement. The system was based on qualifications, experience and earning ability, but in November 2006 the Government suspended the scheme for a month after it was found that some migrants had entered on forged papers, others were working in unskilled jobs and some were not working at all.

A new criterion was introduced where migrants would have to score points based on their education, salary and age. The changes were attacked by the HSMP Forum, which represents those on the Highly Skilled Migrant Programme. It said that the rules were unlawful and a breach of migrants' legitimate expectations.

The High Court granted the forum a judicial review of the Government's decision and ruled that the original system should be honoured for people already in Britain.

Sir George said that the changes were unfair to those already admitted to Britain under the programme and that there was "no good reason why those already on the scheme shall not enjoy the benefits of it as originally offered to them".

He added: "Good administration and straightforward dealing with the public require it. Not to restrain the impact of the changes would, in my judgment, give rise to conspicuous unfairness and an abuse of power."

The court had been told by John Fordham, QC, that the goalposts had been moved for those previously admitted under the scheme. He said it was "a grossly unfair, massive change to the nature of the programme" visited on highly skilled individuals who had left their homes, relatives, friends and jobs and committed themselves to living in Britain.

The ruling comes after a call last year from the Joint Human Rights Committee of MPs and peers for the changes to be scrapped, arguing that it was a breach of the right to respect for home and family life contained in Article 8 of European Convention of Human Rights.

Amit Kapadia, executive director of the HSMP Forum, said: "People left their careers, uprooted their families to come to the UK and settle down. After some time you come up with new rules and say, ‘forget all those promises, now you have to go back to your country'."

Jacqui Smith, the Home Secretary, was ordered to pay the legal costs of the forum and was refused permission to appeal.

The Home Office insisted that the number involved was much lower than the 44,000 figure put forward by the forum. A spokeswoman said that about 16,000 people who arrived under the old rules needed their leave considered under the new rules. She said that 7,000 had had their cases considered and that only 650 had failed.

Liam Byrne, the Immigration Minister, said: "Did we give migrants a big enough warning that the rules could get tougher while they were here? We said yes, others said no. That's why it was right for a judge to take a look at this case."

Chris Huhne, the Liberal Democrat home affairs spokesman, said: "The ruling makes it clear that the Government's decision to change the rules for highly skilled immigrants already working in this country was not only deeply unfair but also completely illegal. The Government must now recognise that you cannot invite people to come here to build lives and careers under one scheme and then simply move the goalposts."

David Davis, the Shadow Home Secretary, said: "It is unfair that skilled workers who have made a commitment to this country should have the rules of the game changed after they have been welcomed."