Government methods for measuring volunteering levels might have overestimated the number of people who volunteer, according to researchers.
Sector think tank nfpSynergy has examined the way the Government carried out its 2008 Citizenship Survey and concluded that vague definitions of what constitutes volunteering might have rendered the results inaccurate.
The Citizenship Survey showed that 73 per cent of all adults had volunteered at least once in the preceding 12 months, and 48 per cent had volunteered at least once a month.
However, nfpSynergy said the definitions were too liberal and meant that activities such as giving directions to a lost person or going to watch a children's football match could be classified as volunteering.
The questionnaire sent out by the Government divided volunteering into 'informal' and 'formal' versions. Informal volunteering included activities such as looking after someone's pet while they are on holiday. Formal volunteering included trade union activity and providing transport to an event.
"In order to get an indication of all the possible volunteering activities, ways of measuring volunteering were drawn up to encapsulate the broadest footprint of activities," said Jonathan Baker, a researcher at nfpSynergy.
"The danger is that broader definitions blur the line, so that joining a social club or driving your children to a football match can see you classed as a volunteer.
"Tighter definitions are needed to establish the true levels of volunteering and to better evaluate Government strategy."
The method could "mask a failure to increase levels of volunteering" despite high levels of government investment, said Baker.
The Government should draw up new figures that differentiate better between formal and informal volunteering activities, nfpSynergy said.
The Cabinet Office did not respond before Third Sector went to press.