Michael Howard has unveiled further details of his plan to impose limits on immigration.

The Conservative leader used a press conference on Tuesday to argue that Britain needs stricter and more diverse work permits.

Under the plans, permits would be based on a points system modelled on an Australian scheme.

There would be separate schemes for those seeking employment and those requesting the right of permanent residency in the UK.

The party also promised to end permit "switching" so that foreign students would  have to leave the country before applying to work.

Howard said a similar recent announcement by the government was "largely pointless" because it lacked a limit on the number of people arriving in Britain.

"Our work permit system is chaotic and out of control," he argued.

"There are no checks to ensure that people leave when their permit expires - leaving the system wide open to abuse."

Principles

Howard also said that a points system was only relevant when used "to set priorities within a limit".

"Our approach is based on three key principles," he explained.

"First, we will meet the needs of the economy while keeping migration at levels which are manageable, acceptable to the British people and do not put undue strain on public services.

"Second, we will give priority to people with the skills Britain really needs. People's grasp of English will be an important factor.

"Third, temporary work permits will no longer be a route to settlement. This final point is critical. A work permit must not be an automatic right to live forever in Britain."

However, the Tory chief refused to speculate as to whether his own father would have been allowed in to Britain under the tougher plans.

Announcements

And he denied that the Conservatives were playing the race card or making repeated announcements on immigration because it represented their best chance of election success.

The Tories received a considerable poll boost last month after making the pledge to impose an annual cap and health checks on immigrants, leading to accusations that they were exploiting racial fears.

Howard said he was "not going to be put off or intimidated from tackling these things by anything Mr Blair or anybody else says".

But immigration minister Des Browne said the policy was "a con on the British people".

"Another day and another Tory re-announcement on immigration. But once again, the Tories have failed to answer the fundamental questions at the heart of their immigration and asylum policy," he said.

"They have committed to halve the immigration and asylum budget which would mean devastating cuts to the protection of our borders.

"You cannot control immigration by cutting the number of immigration officers and by halving the budget of the immigration service.

"Tackling abuse takes more than tough talk. It takes practical measures and strict controls that work. That is Labour's plan. The Tories plan is a con."