“There is clear evidence” of an increase in HIV among gay and bisexual in Wales due to legal highs, officials have said.

In evidence to an upcoming National Assembly committee inquiry into legal highs, Public Health Wales (PHW) warned that “new psychoactive substances” (NPS) have been linked to increased levels of HIV in the gay community.

PHW told the National Assembly’s Health and Social Care Committee: “There is clear evidence of increased blood borne virus transmission in the UK and Wales as a consequence of NPS use.

“Increases have been recorded for HIV and sexually-transmitted infection transmission among ‘chemsex’ party goers where NPS and other drugs are taken over a prolonged weekend period. The parties are usually sex parties primarily between men who have sex with men.

“The lack of knowledge of the content and strength of NPS may result in increased vulnerability to all users due to a lack of inhibition, unexpected effects and duration of effects.”

A Welsh Government spokesman said: “Our Substance Misuse Delivery Plan for 2013-15 includes a number of specific actions to raise awareness of and improve our ability to respond to new psychoactive substances, which are also know as legal highs. This is a challenging and fast-moving area but we remain committed to tackling the issue.”