THEY gained a reputation as slackers, and now Generation X have also been identified as the least industrious lovers of modern times.

According to academic research on sexual habits, people born between 1965 and 1985 have significantly fewer sexual partners and are less likely to be unfaithful than those who came before and after them.

For the baby-boomer generation, sexual opportunity was opened up by the pill. Those born after 1985 are rediscovering sex as sport largely because of the internet.

But, according to Edward Laumann, professor of sociology at the University of Chicago, the emergence of Aids and the divorce boom gave Generation X insecure emotions and more restricted sex lives.

“There was a backlash against their parents’ attitudes, a crisis of confidence,” said Laumann, author of The Social Organisation of Sexuality, a college text-book in America.

His study, based on thousands of interviews, is expected to be released next year. “It’s clear that, while Generation X has sex, obviously, it’s probably not as much or as varied in styles as their parents or today’s teenagers and students,” he said.

According to Laumann’s preliminary findings, about 30% of Generation X-ers have distinctly different sexual habits from their parents or today’s Generation Y; they have “substantially” fewer partners and reject adultery.

Laumann’s findings were backed by Frank Furedi, 60, a sociology professor at the University of Kent. “Those raised in the 1980s are fundamentally influenced by Aids, Margaret Thatcher’s family values and the left’s reborn puritanism,” said Furedi. “I remember, at a dinner party, using the term ‘recreational sex’, which my generation said all the time, and everyone reacted like it was a perversion.”

The term Generation X was first used in the 1960s, but later came to be associated with those entering adulthood in the economic downturn of the early 1990s. In comparison with the liberated 1960s generation, they were sexually restrained.

Jamie Oliver, the gastronomic campaigner who married Juliette Norton, a former model, in 2000, said: “I’ve never been unfaithful, although there were opportunities in the early days when I had loads of birds throwing themselves at me.”

Many men in their thirties say the pursuit is too stressful. “Sex? It’s overrated,” said Justin Lee Collins, 34, presenter of the Channel 4 series The Friday Night Project, who married his second serious girlfriend. “When I was younger I wasn’t good around girls; I used to get physically sick with nerves. Now I’d rather have a beer with my mates than swing in the rafters.” The trait has also been highlighted by David Kamp, a blogger, in the current American issue of Marie Claire, in which he calls his generation “quite possibly the least titillating, least Caligulan people”.

He writes: “Somewhere between the free-love 1970s and today, a curiously chaste breed emerged and a lot of guys my age feel we missed out.”

According to Laumann, this generation built surrogate families among closed circles of friends in their twenties: the benefit was comfort; the cost, sexual opportunity. He said closed social circles – as depicted in dramas such as This Life on the BBC and Friends, the hit American series – curbed sexual adventures because of the problems of introducing a lover into the circle. “There is a lot of frank talk about sex but surprisingly little action,” he commented.

With the perceived decline in the threat of Aids in the West and the rise of the internet, members of Generation Y have rediscovered sexual adventure. Their habits are being studied by Paula England, sociology professor at Stanford University in California, who is tracking the sex lives of 4,000 young people through an internet survey.

“They are distinct from Generation X, more willing to engage in casual sexual behaviour with strangers in semi-public places like parties,” she said.

“More old-fashioned dating may follow after a few hookups, but not necessarily. It is recreational sex again.”

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