LONDON (Reuters) - The number of British people diagnosed as carrying the virus that causes AIDS has reached record levels according to figures released Thursday.

The Public Health Laboratory Service (PHLS) said 2,868 people were diagnosed with HIV last year, up 7 percent from 1999, and that the number was set to rise.

"This is the second consecutive year where we have reported record high levels of HIV diagnosis," said Dr. Barry Evans of PHLS. "We are now two decades into the HIV epidemic, but we continue to see new cases of an infection which is largely preventable. We cannot afford to be complacent about safer sex."

While gay and bisexual men remain the largest HIV risk groups, in the past two years more heterosexuals than gays have been diagnosed as carriers. Evans pointed to the large increase in other sexually transmitted diseases such as gonorrhea as evidence that people were putting themselves at risk of acquiring HIV.

Last month PHLS released figures showing STDs at a 10-year high. There are now more than 20,000 people in Britain diagnosed as having HIV although the Terrence Higgins Trust, a leading AIDS organization, believes that as many as 10,000 more are unknowingly carrying the virus.

"The (latest) figures clearly show that the HIV epidemic in the UK is not going away," a spokeswoman for the Trust said.

"It's therefore vital that HIV prevention work continues to be funded and promoted if we are to slow down the rate of new infections."

One encouraging sign, according to Evans, is that many of the new cases were people infected years ago but who only now were coming forward to be tested.

"This is positive because once people come forward they can be offered treatment," he said.

The majority of heterosexual infections were acquired abroad by visitors to, or people from, areas of high prevalence such as sub-Saharan Africa.