The Disasters Emergency Committee's Haiti Earthquake Appeal has raised more than £25m in its first few days.
The committee, made up of 13 UK-based international aid charities, opened its appeal overnight on Thursday.
It has raised the sum through donations made online and over the phone, and expects to receive postal donations and donations from businesses in the next few days.
The appeal raised its first £8m after the committee announced the start of the appeal on Twitter. At 7.41pm on Wednesday, the DEC sent a message to its followers on the social networking site saying: "You're the first to know - DEC #Haiti Earthquake Appeal now live, UK broadcast appeals to follow."
The opening of the appeal was followed at midnight on Thursday by the 'period of joint action', during which DEC member charities are obliged to offer donors the chance to donate to the DEC instead of directly to the charities.
A spokesman for the DEC said the BBC website drove the most supporters to its website, followed by social networking sites Facebook and Twitter.
He said the DEC's Facebook page had 800 fans before the earthquake last Tuesday, but 10,000 by Sunday morning.
Brendan Gormley, chief executive of the DEC, said: "Almost a week on from the earthquake that hit Haiti, we have been staggered by the generosity of the UK public.
"Over the past week, DEC partner agencies have been working round the clock to meet the needs of the Haitian people."
The magnitude 7.0 quake struck on 12 January about 10 miles from the Haitian capital, Port-au-Prince.