Scientists at Birmingham University are calling on the Government to actively screen men for chlamydia.
A national screening programme already targets women when they attend a GP surgery or family planning clinic - but not men.
But a study led by Dr John Macleod, examining the prevalence of chlamydia through a postal screening project, found just as many men as women had contracted the sexually transmitted disease.
Chlamydia has no real symptoms but carriers can develop pelvic inflammatory disease and in women it can damage the fallopian tubes, leading to the risk of an ectopic pregnancy.
Researchers from Birmingham University and Bristol University invited 19,773 men and women, selected randomly from records at 27 GP surgeries, to take part in a postal screening scheme.
Each was asked to send a urine sample in for testing, and the results showed chlamydia to be most common in people under 25.
Within that age group, five per cent of men tested positive for the disease, compared to 6.2 per cent of women.
Dr Macleod, who is also a city GP, said he hoped the Government would review the current screening programme to actively test men as well as women.
"The Department of Health has rolled out this national scheme but in places it's still very patchy because GPs don't get paid to do it," said Dr Macleod.
"Because it's a disease that doesn't get reported early, as there are no obvious symptoms, by the time anything is noticed - especially in women - it can be too late, the damage is already done.
"If men aren't being screened, half the population is effectively being ignored and that's a big risk to take.
"They tend to only seek help if advised by their partner that they may have chlamydia.
"This also suggests it's not the man's responsibility to take care of his sexual health - which is wrong, surely?"
The study, published in the British Medical Journal , also found that 16 to 24-year-olds and people living in areas with high ethnic populations were least likely to go for the test.
Dr Macleod said the Government's system was missing patients who do not have regular check-ups, who are usually those most at risk.
He said: "The current scheme only reaches women who go to see their GP or family planning clinic, but really what we need to do is focus on those not going for check-ups.
"No reminders are sent out to patients, like with the national cervical screening system.
"We certainly picked up some people through this postal trial that the Government's opportunistic system would have missed.
"Because chlamydia is almost as common in men as it is in women, they must be included in any national screening programme. Unfortunately that is not what happens now.
"Perhaps a mix of testing within GP and family planning clinics and the postal screening scheme would enable more people to be tested.
"Either way the system needs to be improved because it's missing too many people at the moment."