Fewer than half of people in the UK are having sex at least once a week, a major new study has found.
Social media, stress and family life getting in the way have been cited as the main causes for this downturn in sexual habits.
While young British men aged 16 to 25 get the most, the most sex-starved are those in early middle age or married or cohabiting couples.
Between 2001 and 2012, both straight and gay Britons have been less active between the sheets, with the numbers going without sex for a month increasing to three in ten men and women.
The number having sex 10 times or more a month dropped too, with only around a sixth of men and an eighth of women saying they achieved this, the BMJ revealed.
Despite the fall in having sex, little was known about these trends in Britain and the lifestyle factors associated with them.
So researchers used data from more than 34,000 men and women aged 16 to 44 years in three successive waves of the British National Survey of Sexual Attitudes and Lifestyles completed in 1991, 2001 and 2012.
The surveys reported sexual activity including vaginal, anal, or oral sex with straight or gay partners.
It found the proportion who had no sex in the past month from 2001 to 2012 increased from 23 per cent to 29.3 per cent among women and from 26 per cent to 29.2 per cent among men.
The proportion having sex 10 or more times in the past month also fell from 20.6 per cent to 13.2 per cent among women and from 20.2 per cent to 14.4 per cent among men.
A lack of sex affected all age groups for women and men over 25 - but the decline was more marked in the over 25s, married couples or those living together.
The average number of times those aged 35 to 44 had sex in the past month fell from four to two among women and from four to three among men.
The odds of reporting sex 10 or more times in the past month halved.
Single people more sexually active
Similarly those who were married or living together reported higher sexual inactivity in the last month while the odds of reporting sex 10 or more times in the past month were roughly halved.
But single people fared better, suggesting the trend towards lower sexual frequency overall is largely due to the decline among sexually active married or cohabiting couples.
The study found close to half of all women (50.6%) and almost two thirds of men (64.3%) said they would prefer to have sex more often, particularly those who were married or living together.
People in better physical and mental health, and those who were fully employed and had higher incomes, reported having sex more often.
Why are people having less sex?
The lack of sex could be because we are now distracted by social media or because we had to tighten our belts after the 2008 recession - which may explain the decline both among men who are better off and those worse off.
But stress and being too busy juggling work, family life and leisure were most likely the culprit for us not getting enough.
Professor Kaye Wellings of the London School of Hygiene & Tropical Medicine explained: "Several high income countries have recently reported a decline in the frequency with which men and women have sex.
"Sexual inactivity might not seem an obvious focus for public health attention - concern is generally reserved for sexual activity and its adverse outcomes such as unintended pregnancy, sexually transmitted infection, and sexual dysfunction - but regular sexual activity has benefits for health, wellbeing, and quality of life.
"Research indicates that men and women who enjoy an active sex life are fitter, happier, and have better cognitive function and increased life expectancy.
"Evidence shows that sexual activity might help prevent infection by bolstering immune function, protect against cardiovascular disease by lowering heart rate and blood pressure and reduce stress by increasing release of oxytocin."