Just nine out of 650 members of Parliament (MPs) currently donate to charity directly from their pay, up from four out of 646 in 2008.
The information was gathered through a Freedom of Information request by Geared for Giving.
Payroll giving, a scheme introduced in 1987, enables UK employees to donate to charity from their gross pay before tax is deducted.
On 24 January, the government launched a consultation on proposals to reform the payroll-giving scheme, including simplifying its administration and making it easier for employees to donate through payroll.
Peter O’Hara, managing director at Workplace Giving UK, said: “It is hugely disappointing that so few MPs use the scheme; it is by far the most tax-efficient way for employees to donate to their chosen cause, especially so for the higher-rate tax payer, which all MPs are.
“Giving straight from their pay will ensure an extra 40% of donations will get to their favourite cause, whereas giving via a direct debit and ticking a Gift Aid box will only allow their cause to claim back standard-rate tax.
“We know that many MPs give to good causes in other ways, however, given the benefits to charities and tax efficiencies that payroll giving offers, we would like to see MPs set a real example.
“It is unacceptable that so few give from their pay. We believe that, like many other employers, the government has not communicated the scheme effectively and so we are calling on [prime minister] David Cameron, deputy prime minister Nick Clegg, Labour party leader Ed Miliband, [chancellor] George Osbourne and all MPs to show the way and not only sign up to the scheme but also to take the message out to constituents.”
The Independent Parliamentary Standards Authority (IPSA), which monitors and controls MPs’ expenses, pay and pensions, declined to comment.