Many Britons have problems when it comes to sex, according to a study.
The problems cause many people to avoid having sex
Research, published in the British Medical Journal, suggests one in three men and half of all women may be affected.
Among men, the most common problems are a lack of interest in sex, premature ejaculation and anxiety about their performance in the bedroom.
Women reported a loss of sexual desire, an inability to reach orgasm and pain during intercourse.
The findings are based on two studies by researchers at University College Medical School in London.
The first surveyed 1,065 women and 447 men attending GP clinics in the capital.
It found that 22% of men and 40% of women had been diagnosed with a sexual problem.
However, the second study - a national survey of sexual attitudes and lifestyles involving more than 5,000 people - found 35% of men and 54% of women had at least one sexual problem.
These problems lasted for at least one month. However, for 6% of men and 15% of women the problems lasted at least six months.
One in three men and two out of three women said their problems were so bad they avoided having sex.
The studies show that many people are reluctant to seek help or treatment if they have a sexual problem.
The first study on patients attending GP clinics found one in three had talked to their doctor about their problem.
However, the nationwide survey found that just one in 10 men and one in five women sought help.
The authors of both studies said their findings highlighted the need for improvements in the way sexual problems are dealt with in Britain.
"Our data have implications for improving relationship education, counselling, medical education and doctors' professional development," they said.
On the increase
Denise Knowles, a sex therapist and member of the UK charity Relate, said she was not surprised by the findings.
She said sex problems were on the increase and suggested that some of these may be related to people's lifestyles.
"People in this country work some of the longest hours in Europe. An awful lot of people also feel insecure about their jobs.
"When they get home, many are exhausted. This combined with not feeling secure is not conducive to wanting to have sex," she told BBC News Online.
"We are also seeing a rise in obesity, diabetes and heart disease. These conditions can also affect people. Testosterone levels are also said to falling and these give us our sex drive."
Ms Knowles said that being able to have a good sex life is important.
"For some couples, it is the most important part of their relationship. For others, it is a bit further down the agenda.
"But a loving sexual relationship has real benefits, physiologically and psychologically. As human beings we need to be touched."
She said people with sex problems should seek help.
"One thing we cannot do is make someone fancy someone again but if the relationship is generally good we have every chance of creating an environment where these problems can be overcome."