Sexual disease clinics are failing to tackle the UK's rising cases of sex infections, warn doctors.
Targets are not yet being met by sexual health clinics
Current inadequate capacity is creating a vicious cycle where failure to treat infections promptly allows them to spread further, they say.
In the Journal of Infectious Diseases, the Imperial College and University College London teams call for a big increase in capacity.
The government said it was working hard to improve access to clinics.
However, it said it would take some time for these efforts to produce the desired results.
The number of sexually transmitted infections (STIs) recorded in Britain has doubled in five years.
The government has pledged that by 2008 patients will be seen at genitourinary medicine (GUM) clinics within 48 hours.
Figures from the Health Protection Agency show that last year only 41% of people attending GUM clinics were seen within the recommended 48 hours, and 26% were not seen within two weeks.
This delay can lead to increased infections, and a further increase in demand on already overstretched services, the London-based researchers say.
Lead researcher Dr Peter White said: "Current levels of capacity have failed to keep up with increasing demand, resulting in yet more infections as many people are unable to get treated promptly or even at all, in some cases.
"Our work has shown that a significant increase in capacity is needed to tackle the current epidemic.
"This would be an investment, with the pay-off that it would reduce the number of infections that occur in the future, and would reduce rates of complications like infertility, which are costly to treat."
Dr Angela Robinson, president of the British Association for Sexual Health and HIV warned: "With waits of up to eight weeks for a routine screen for STI in some parts of the country and some people being turned away who may never get seen, STIs will continue to rise until capacity is increased sufficiently in specialist services with the experience to deal with cases efficiently and speedily."
A spokeswoman from the Department of Health said: "We recognise there is still a long way to go before we meet our 2008 target.
"We have responded to this by committing an extra £130m for GUM services between 2006 and 2008 - allowing clinics to expand their services and offer more and more people access to early treatment."