The widely held view that volunteers are predominantly older women with a lot of time on their hands is a myth, says a report that suggests it is 25- to 34-year-olds who dedicate the most time to unpaid work.

In a damning survey of charitable attitudes among different age groups, a third of Britons said nothing would persuade them to leave the comfort of the sofa or the warmth of the pub in order to make a difference in their community. This figure rose to 47% of over-55s – compared with just 12% of 18-24s.

Younger people were doing more good work, with the 25-34 age group bearing most of the burden of volunteer work. The number of hours spent volunteering is higher in younger age groups: those under 35 said they spent an average of two hours a week volunteering, compared with the hour that over-55s claimed to spend.

Dan Jones, director at the innovation charity Nesta, which carried out the research, said the notion that the “baby boomer” generation wouldn’t volunteer was a “real worry” for the sector. “The voluntary and charitable sector really relies on those over-50s with a bit more time on their hands,” he said. “If people now hitting that age range aren’t going to be helping in their community but just thinking about themselves and going to Alicante, or whatever, we’ve got a challenge ahead.”

He said younger people recognised the value of charitable work: “They see it as a win-win: giving back, helping their own CVs and making an impact.”

The research, to be published this week, found that, on average, the public spend one hour 47 minutes volunteering each week, compared with 12 hours 40 minutes watching TV, nearly three hours commuting and two hours in the pub. (Respondents spent less time in the gym – one hour 28 minutes – and queueing for coffee – 45 minutes.) Men were more likely than women to help an elderly neighbour: 34% compared with 30% of women.

Respondents believed the average volunteer to be female, over 60 and a grandparent, which used to be the case, said Jones. “Earlier surveys showed that about 40% of people volunteered once a year and 25% once a month,” Jones said. “It’s always been the case that women volunteer more than men so it’s striking to see the swapping over in the trends. Women have always been the backbone of volunteering in the UK.”