The number of hours people in the UK spent volunteering each year fell by 15 per cent between 2005 and 2015, according to the Office for National Statistics.
In 2005, 2.28 billion hours were spent engaged in formal volunteering, but by 2015 this figure had fallen to just 1.93 billion hours, data published today reveals.
The figures, taken from the ONS Community Life Survey, do not include an estimate of the cost for the entire period, but the document says the 7 per cent fall in the number of volunteering hours between 2012 and 2015 cost the UK an estimated £1bn-plus.
The average time each person puts into volunteering has also fallen, from a mean average of 14.5 minutes per volunteer each day in 2005 to 13.7 minutes in 2015, according to figures published in the same document from the ONS analysis of the Harmonised European Time Use Survey.
This equates to a drop from a weekly average of one hour, 42 minutes to one hour, 36 minutes.
Data from the Community Life Survey shows that participation rates in formal volunteering increased, with 39 per cent of both men and women doing some form of volunteering in 2005, and 41 per cent of men and 42 per cent of women participating in 2015.
But the actual time men spent volunteering fell from 12.3 minutes a day in 2005 to 11.3 minutes in 2015. For women, the figure dropped from 16.3 minutes to 15.7.
Despite this, volunteering by people aged between 16 and 24 has increased since the turn of the millennium. In 2000, 40 per cent of this age group participated in volunteering, giving an average of nine minutes a day; by 2015 this had increased to 51 per cent participating for an average of 17 minutes a day.
But in the next age category, those aged 25 to 34, people appear to have more than halved their time spent volunteering, from 14.5 minutes a day in 2000 to just six in 2015.
The ONS statement on the data said: "It could be that, as younger people try and secure employment, they undertake voluntary work in order to enhance their CVs, but as they embed themselves in their careers, at an older age, their focus turns to building their careers."