Only 20 per cent of people in a government survey said they had used Gift Aid for their charitable donations in the past year.
Of those involved specifically in planned giving, 43 per cent had used Gift Aid or other forms of tax relief.
The use of tax-efficient giving would increase if there were greater efforts to publicise how simple it is, the study concludes.
But an increase in tax-efficient giving would be unlikely to produce an increase in the amount given, which has remained unchanged for 17 years.
The research, which was carried out last year, has just been posted on the HM Revenue & Customs website. Publication was delayed by the General Election.
An opinion poll backed by in-depth interviews found that people who had not used tax relief were not against doing so on principle.
The report says: "People said they had not got around to it, that they gave only occasionally and that they thought tax relief applied only to regular donations."