All immigrants entering the UK should be screened for infectious diseases, the Tories have said.
Immigrants would be tested for HIV and TB under the Tory plans
The UK is "building up a frightening level of hidden illness" and compulsory screening is essential to prevent them being brought into the country, said shadow health secretary Liam Fox.
It would also stop people coming to Britain simply for free
health care, draining the resources of the NHS, he said.
The plan, outlined in a Conservative Party consultation paper, has been condemned as "extremist" and "unworkable" by politicians, refugee groups and health workers.
The paper, called "Before It's Too Late: A New Agenda for Public Health", proposes the adoption of an Australian-style system of screening immigrants for HIV and tuberculosis at the point of application.
Immigrants would have to pay for the tests and asylum seekers would be detained until it was clear the tests had been met, it said.
This is an unnecessary, extremist, unethical and unworkable policy
Liberal Democrat health spokesman
The document said more than 50% of TB in the UK now occurs in people born abroad, the majority of whom arrived in Britain within the last 10 years.
It called this an "avoidable scandal" caused by "political cowardice and charges of racism".
Dr Fox said he realised the suggestion was controversial, but said the issue had to be tackled by mainstream politicians in a "responsible and rational way" or could be hijacked by far-right groups.
'Poorly thought out'
The Joint Council for the Welfare of Immigrants said the idea appeared to be ill-thought out and "completely unethical".
Chief executive Habib Raham told BBC News Online there was "no substantial evidence" that asylum seekers were more likely to have HIV or TB than anybody else.
"This seems to be spreading fear in people and scapegoating a very vulnerable section of the community", he said.
Doctors' union the British Medical Association (BMA) also said the suggestions were "poorly thought out".
Dr Vivienne Nathanson, head of ethics at the BMA, told BBC News: "It may well be seen as a burden on the health service but the fact is, that isn't the reason primarily that people will come to the UK.
"And the fact that they have a condition which may need treatment doesn't mean that they are necessarily a burden to us in general. They may well bring skills that we particularly need."
She suggested that rather than focus on "perceived threats from abroad", the Tories should look at the most serious public health issues facing the UK, including cancer, coronary heart disease and the impact of smoking.
Derek Bodell, chief executive of the National Aids Trust, said HIV screening could in fact backfire and prove ineffective.
"The danger is people go underground and don't come forward for testing."
Canada and the US, which have such screening, had "not been able to keep control of it", he said.
And he pointed out that a policy workable in Australia - "miles from anywhere" - would not translate to European countries with millions of people coming and going over borders.
Instead, he suggested, the UK should continue with its policy of encouraging people to come forward voluntarily for HIV testing and treatment - and improve its sexual health education.
The government was reported in the Times earlier this year to be considering HIV screening for immigrants.
A Home Office spokesman said on Monday that a Cabinet Office review into the whole issue was "ongoing", with no dates as yet as to when it would report back.
The proposal was strongly condemned by the Liberal Democrat health spokesman Evan Harris as "unnecessary, extremist, unethical and unworkable".