Printed by Brightsource, the simple doubled-sided A4 text only piece was sent to 46,000 supporters of the charity Crisis in April.

Crisis, direct marketing executive Raj Dasani, said that the direct approach has been very effective: "We saw the response rates double. We had something like 10% rather than 5%".

The campaign has raised £150,000 against its target of £100,000. Dasani said Crisis was sending out follow-up mails to those who hadn't responded and expected the figure to grow, although he said it is unlikely to cover the charity's entire £350,000 deficit on last year's donations.

"We've still not filled in the gap, but it shows how individual supporters can respond and help," he said.

He said that an email shot to 2,500 people was also included in the campaign, but this only achieved a 0.2% response.

"We're not getting email to work that well – I don't think many charities are making email work that well," said Dasani. "We never find it works better than print."