Immigrants to the UK could speed their progress towards British citizenship in future - by returning to their home country, by becoming actively involved in the civic life of the UK or by choosing to settle in Scotland.

The measures are contained in the Borders, Citizenship and Immigration Act, unveiled yesterday, that would earn people bonus points in a tough, new "earned citizenship" regime for the 150,000 who apply for a British passport each year.

The Australian-style points-based system, launched by immigration minister Phil Woolas, also proposes harder language and history tests at the end of a probationary period of living in Britain before full citizenship can be awarded.

Migrants could be given extra points for their skills, jobs and qualifications, while crime, antisocial behaviour, or "failing to integrate into the British way of life", which some fear might include political activism, would cost them points.

The government is also looking at giving points to people waiting for citizenship, who take skills back to their country of origin and carry out development work, to help their chances of becoming British when they return to the UK.

The consultation document, entitled Earning the Right to Stay, aims to break the automatic link between coming to the UK temporarily to work or study and staying permanently.

Under the proposals migrants will have to spend five years in the UK as temporary residents, before becoming "probationary citizens". They can then earn full citizenship by earning points - a process that is expected to take between a further one and five years.

"Civic activism" - such as being a school governor or "contributing to the democratic life of the country through trade union activities or canvassing for a political party" - could reduce the process from three years to one.

Mr Woolas said the proposals were designed to control immigration and help integration, after admitting that some areas of the country had been "overburdened" by migrants.

Ministers say the changes will enable them to control the numbers of people becoming citizens, by moving the qualification bar up or down.

Mr Woolas said: "We are going to introduce these proposals to make sure we can control migration to bring better confidence to the public and, of course, control the impact of migration."

The proposals were dismissed as "pure spin" by the Conservatives but measures to give weighted points for migrants willing to settle in Scotland, where population levels are in long-term decline, were welcomed by the SNP as "a move in the right direction".

The well-trailed idea of giving applicants a higher score if they have set up home in Scotland has been defended by Scottish Secretary Jim Murphy as a tool for economic development.

SNP Home Affairs spokesperson Pete Wishart MP also welcome the priority given to Scotland but repeated calls for powers over immigration to be devolved to Scotland just as they are in Australia's states. "Scotland's population and immigration requirements are completely different from the rest of the UK, and this has to be recognised when points are added up," said Mr Wishart.

"Such a system is already working successfully in Australia, where different State Governments can grant visas to live and work in that state alone. UK ministers have adopted the Australian system, but without the key flexibility component that would allow Scotland to tailor its immigration requirements."

Tory immigration spokesman Damian Green said: "The Labour Government's open-door immigration policy has not benefited the UK, nor the countries of origin hindered by brain drain'. These proposals are tinkering at the edges of a far wider problem. It is time to get a grip on the consequences caused by unlimited immigration."

Liberal Democrat home affairs spokesman Chris Huhne said tinkering with the system would not deal with "hundreds of thousands of illegal immigrants living here."

He added that in barring people for unpatriotic behaviour, it looks as if the government wanted to play the Thought Police.