Campaigners are urging the government to close a legal loophole that could allow employers to refuse jobs to applicants on the basis of genetic tests.
Some fear jobseekers could be subjected to a genetic test
They say that without appropriate safeguards a "Brave New World" of genetic testing could emerge in the workplace.
People with adverse genetic test results but no symptoms are not protected by the existing Disabilities Discrimination Act.
The TUC, Genewatch UK and the British Council of Disabled People (BCODP) said the loophole should be closed urgently, although it is not believed that any UK employers are currently using the tests.
The campaigners say picking and choosing workers to suit hazardous environments or cut pensions costs would be totally unacceptable.
But there is evidence that the tests may have some support among employers.
In 2000, an Institute of Directors (IOD) report found 50% of employers thought it would be appropriate to conduct genetic testing "to see if employees are at risk of developing an occupation-related disease due to exposure in the workplace".
One third of those interviewed thought it would be appropriate "to see if they will develop heart disease which might affect sickness or early retirement".
However, the IOD said only 16% expressed any interest in using genetic testing.
"We really want to stress that the 50% is under very strict circumstances.
"It only really concerns whether an employee is susceptible to a disease because of the nature of their work," said a spokesman.
"You don't want to put them in a situation where they could be in danger of getting a disease."
The warning comes at a time when the Human Genetics Commission (HGC) meets to consider the government's response to recommendations on genetic discrimination.
TUC General Secretary Brendan Barber said: "We want the government to make sure everyone has an equal right to succeed at work, whatever their genetic inheritance.
"We should be promoting opportunities for all, not penalising people because of their genes."
The Department of Health said in a statement that it will look into Genewatch's report.
"In the Genetics White Paper... published in June this year, the government gave a commitment to consider the evidence for unfair discrimination against people on the basis of their genetic characteristics and the appropriate means of addressing any concerns in this area."