The UK has one of the highest rates of HIV infection in Europe largely due to a growing epidemic of the disease in the black African community and among gay men, the Health Protection Agency (HPA) warned today.

The sexual health crisis is also worsening due to rising rates of other sexually transmitted infections (STIs) among young adults, the government health watchdog also warned.

There were 376,508 diagnoses of new STIs in 2006 - up from 368,341 in the previous year, said the HPA, which monitors infectious diseases in the UK.

Young people aged 16-24 accounted for the majority of new cases of some of the most common sexually transmitted infections, despite concerted efforts to encourage them to practise safer sex.

Last year, young adults accounted for 65% of all new cases of chlamydia, 55% of all genital warts cases and 48% of cases of gonorrhea. One in 10 of the 14,939 young adults tested in the national chlamydia screening programme in England tested positive for the disease, which is linked to infertility.

The findings came as a separate report found that the UK had one of the highest rates of new HIV infections in Europe last year.

The report by the European Centre for Disease Prevention and Control (ECDC) found the UK HIV infection rate was more than double the European Union average - almost 149 cases per million inhabitants compared with an EU average of 67 cases per million.

The ECDC found that HIV/Aids cases in Europe have doubled in six years, bucking the trend elsewhere in the world where infection rates have fallen.

Three-fifths of new HIV infections diagnosed in the UK last year were acquired abroad, according to the HPA. Black Africans accounted for half the total number of new HIV infections last year. More than four-fifths (84%) of them contracted HIV in Africa.

There has been a fivefold increase in HIV infections in black Africans since 1997.

The HPA, which monitors infectious diseases in the UK, also raised concern about the "disturbing" rise in HIV among gay men.

There were 2,700 new cases of HIV in this group last year, breaking the previous record high of 2,650 set in 2005. There were 31,100 gay men living with HIV in the UK last year - more than 40% of the total number of people infected, which is 73,000.

Rates of other STIs in gay men have also risen dramatically in recent years, which the HPA blamed on a growing failure among this group to practise safer sex.

Between 2002 and 2006, rates of newly diagnosed gonorrhoea rose by 25% in gay men, syphilis by 117%, chlamydia by 97%, non-specific urethritis by 24% and genital warts by 21%.

Dr Valerie Delpech, the head of HIV surveillance at the HPA, said: "In recent years we have seen steady increases in all sexually transmitted infections, including HIV, in gay men and since 2003, the number of HIV diagnoses reported annually has consistently increased and exceeded the annual number of diagnoses throughout the 1980s and 1990s."

Professor Pete Borriello, the director of the HPA's centre for infections, said it was imperative to get across the importance of practising safer sex, particularly among high-risk groups such as gay men and young adults.

He said: "We recommend that gay men should have regular HIV tests, STI clinic attendees should be tested for HIV at every visit and young sexually active adults should be screened for chlamydia annually and after a partner change.

"We need to reinforce the safe sex message for gay men, young adults and the broader community. The best way to protect yourself from contracting an STI including HIV is by practising safer sex by using a condom with all new and casual partners."