The immigration minister, Barbara Roche, said in a speech in Paris yesterday that the government believed it was time to start a debate on finding ways to meet "legitimate desires to migrate" to Britain and called for an "imaginative rethink" of existing immigration rules so migration could meet economic and social needs.

She wanted to see "innovators with good ideas to take the economy forward" and add to national wealth, as well skilled specialists come to Britain.

It is thought that ministers are more inclined to an extension of the current overseas workers scheme which enables some specialists in shortage occupations to work in Britain rather than a major relaxation of the 1971 Immigration Act which effectively bans primary immigration.

The Home Office is believed to be looking at a limited version of the Canadian scheme under which 200,000 migrants will enter Canada this year.

Mrs Roche's speech, which was to have been delivered by Mr Straw, marked a sharp departure in tone for government ministers who, while they have stressed the positive benefits of immigration to Britain, have tended to concetrate rather more on the abusive claims of some asylum seekers and the criminal gangs who operate behind them.

Mrs Roche made clear yesterday that she believed the two issues of asylum and immigration had to be treated differently and separately. The government's approach to dealing with skilled workers who could benefit the economy could not be dictated by the need to clampdown on the racketeers who smuggled illegal migrants into the country.

"Our thinking on these issues is now developing," she said. "It is clear throughout the centuries immigrants have had a very positive impact on the societies they join. I welcome the debate and will want to play a full part in it."

The Canadian scheme enables professionals and skilled workers to get a permanent resident visa in Canada even if they do not have a job offer from a prospective employer. To qualify, a potential migrant has to have a minimum of 70 points based on occupation, education and training, experience, age and knowledge of English and French. For example, those who are between 21 and 44 get a maximum of 10 points but those under 18 or over 48 get zero for age. A university degree ranks as 16 points, a validated job offer 10 points, personal suitability based on an interview up to 10 points, five points for a relative in Canada and so on.

Ministers believe this is fairer than the green card system operated in the US. Occupations which attract the most points in Canada include computer programmers, physiotherapists and sous-chefs.

Immigration welfare groups welcomed what they saw as the "first faint stirrings" of signs that the government may at last be putting the asylum issue into the sensible context of the pressures faced by economic migrants.