Asylum seekers should be barred from using the NHS to prevent health service overstretch, Migration Watch has said.

In a controversial move the migration think tank has called for UK citizens be given entitlement cards to access medical treatment.

Illegal immigrants, who total up to one in 20 Londoners, would then be locked out of the NHS freeing up resources of up to £600 million a year.

Successful asylum seekers or refugees would not be excluded from hospitals or doctors' surgeries.

The anti-immigration pressure group denies that such a policy would be "racialist". Its founder, Sir Andrew Green, argues that ignoring the issue fuels the far-right.

"This is absolutely not a question of racialism, but of realism," he said.

"This issue has been ducked too long and must be tackled. We must not leave the field open to those - particularly on the far right - exploiting people's concerns for their own ends."

Sir Andrew's warning that "immigration at this rate will have a profound effect on the nature and shape of our society for decades to come" has, however, been welcomed by those on the racist right.

"Migration Watch UK's findings confirm what the BNP has been saying for the last ten years. Immigration is out of control and must be stopped if our British way of life is to be maintained," says the British National Party website.