Money worries and the distractions of social media mean people are having sex less frequently, researchers say.
A once-a-decade poll of 15,000 Britons found those aged 16-44 were having sex fewer than five times a month.
The figure compared with more than six times a month on the last two occasions when the official National Survey of Sexual Attitudes and Lifestyles was carried out, in 1990-91 and 1999-2001.
The study’s authors say modern life may be having an impact on libidos.
Dr Cath Mercer, from University College London, said: “People are worried about their jobs, worried about money. They are not in the mood for sex.