The number of people being diagnosed with sexually transmitted infections (STIs) is now at record levels.
The government launched a fresh campaign last year
Doctors have warned ministers they risk having a major public health crisis on their hands unless they take urgent action to tackle the problem.
STIs have jumped sharply in recent years. Syphilis has risen by 486% since 1996. Chlamydia is up by 108% over the same period and rates of gonorrhoea are 87% higher than they were seven years ago.
More people are also being diagnosed with HIV. In 2001, a total of 4,419 people were told they had the virus, up 17% on the previous year. The number of new infections is predicted to double between 1997 and 2005.
An estimated 40,000 people living in Britain are now HIV-positive. As many as one in three of these do not realise they have the disease.
There is no clear explanation for the sharp rise of recent years. For instance, there is little evidence to suggest it can be attributed to more people engaging in casual sex.
"Changes in sexual behaviour are not sufficient to explain the increase in sexually transmitted infections," says Dr Roger Ingham of the Centre for Sexual Health Research at the University of Southampton.
"It may be the case that more people are engaging in casual sex. However, the rise in STIs is so high that it cannot be explained by this."
HIV: 4,419 cases - up 17%
Syphilis: 715 cases - up 119%
G'rhoea: 22,697 cases - up 7%
Chlamydia: 71,125 - up 10%
Herpes: 17,850 - up 5%
Warts: 67,672 - up 2%
Increase in 2001 compared to 2000
The most obvious explanation is that people are simply failing to practise safe sex.
However, even this isn't clear cut. Teenage pregnancy rates are falling suggesting that more couples are using contraception.
Recent studies have also found that more people are using condoms when they first have sex.
Problems appear to be linked to the choice of contraception. While more teenage girls may be taking the Pill or emergency contraception, the statistics suggest they are not using condoms. Condoms are the most effective way of preventing the spread of STIs.
In addition, there is evidence to suggest that couples put themselves at risk by deciding to stop using condoms when their relationship becomes more stable.
"Our research shows young and older people are finding it difficult to maintain condom use once they are in a trusting relationship," says Dr Ingham. "Obviously, if there is a STI it can then be transmitted."
The sharp increase in STIs suggests that couples are becoming more complacent and are not listening to calls to practice safe sex.
"In the late 1980s and early 1990s, we had campaigns warning people about HIV. They also helped to prevent STIs," says Derek Bodell, director of the National Aids Trust.
We don't talk about sex
Simon Blake, Sex Education Forum
"While there have been some new campaigns, overall there hasn't been the same level of promotion. Increasingly, generations are coming forward who have not heard about HIV and who do not know much about using condoms. They are missing out on the key messages," he says.
This is compounded by the fact that many people have major misconceptions about STIs and HIV. A study published last year suggested one in three 18 to 24 year olds wrongly believed there is a cure for HIV.
Cultural issues also play a part. Many people are simply too embarrassed to talk about sex, let alone STIs, with their friends or family.
"We don't talk about sex," says Simon Blake, director of the Sex Education Forum.
"A lot of people have feelings of embarrassment, shame and guilt around sex. People also do not access sexual health services or get the support they need.
"We need to raise awareness and to tell people that STIs are still around and that HIV is still here."
The government published a 10-year-plan to improve sexual health in July 2001. The National Strategy for Sexual Health and HIV Services was backed with £47.5m.
However, that money represents a mere drop in the ocean. According to doctors, it won't even cover the cost of implementing a national screening programme for Chlamydia let alone improve services elsewhere.
"Sexual health is not an NHS or political priority," says Professor Michael Adler, chairman of the group which drew up the strategy. "It is no exaggeration we now face a public health crisis in relation to sexual health."
Sexual health is not an NHS or political priority
Experts believe that the situation will fail to improve unless sexual health becomes a government priority.
"A lack of prioritisation is making it very difficult for charities, local hospitals and primary care trusts to deliver the services which are so badly needed," says Colin Dixon of the Terrence Higgins Trust.
One of the major problems is that money for sexual health services is allocated at a local level. In many areas of the country, it comes a long way behind other health priorities such as fighting cancer and heart disease.
As a result, many sexual health clinics are struggling to cope with demand. While clinics have seen their workload increase by 155% over the past 10 years, their budgets and staff levels have largely remained the same.
Patients are often forced to wait days for an appointment and sometimes weeks for treatment even after they have been diagnosed with a STI.
"Clearly, if you have someone who has a STI then diagnosis and ease of access for patients is crucial in preventing it from spreading," says Derek Bodell.
"Some professional associations have suggested that as many as 150,000 people are waiting to be seen at sexual health clinics at any one time."
These delays increase the risks of people passing on infections, according to the Liberal Democrats.
"People are turned away from overloaded sexual health clinics, remaining at risk to themselves and to others," says Patsy Calton, its health spokeswoman.
The Department of Health insists that its 10-year strategy will deliver improvements.
"Teenage pregnancy rates have come down over the past three years," says Dr Roger Ingham.
"We would hope that given the same time, we will see similar improvements in STIs."