Tory plans to withdraw Britain from the 1951 convention on refugees have been condemned as "unworkable" by the UN and EU.

Party leader Michael Howard yesterday set out his plans to set quotas for immigrants and asylum seekers, prompting warnings that his controversial policies would isolate Britain.

Howard gave details of how the proposed quota system would work, as well as suggesting an Australian style points system for migrants and a bar on asylum applicants making claims from inside the UK.

Insisting his ideas were common sense and not racist, he set out a phased programme to rewrite Britain's immigration laws.

He said a Conservative government would give the UN secretary general 12 months' notice of withdrawal from the 1951 convention on refugees.

The government would then meet its annually set quota of refugees by selecting "genuine" applicants from those in the care of the United Nations high commissioner for refugees (UNHCR).

"There are literally millions of people in other countries who would like to come and live here," he said. "Britain cannot take them all."

However, Brussels officials said that directives already signed by the government would prevent the Tories from adopting a go-it-alone policy.

Tony Blair has condemned the proposals.

The prime minister said yesterday: "Every wealthy country around the world faces the same problem. More people are coming in and out of the country for perfectly legitimate reasons, to work, to study and visit. But there are abuses of the immigration system.

"The real point about the Conservatives' proposal is that by cutting the number of front-line immigration staff at our borders, they will actually make the problem worse.''

The Independent claims that under the Tory plans, prominent Britons including Olympic gold medallist Kelly Holmes and Mike Fuller, the chief constable of Kent, would not have been able to live in the United  Kingdom.