Donations from the British public to help flood victims in Pakistan have reached £29 million, the Disasters Emergency Committee (DEC) said.
Chief executive Brendan Gormley said it was the first time that donations had risen in the second week of an appeal.
"The UK public are leading the way and shaming politicians across the world," he said. "We want the rest of the international community to back that sustained giving."
The worst floods to hit the country in decades have left more than 1,500 people dead and an estimated 20 million homeless.
An appeal to help the stricken country was launched two and a half weeks ago by DEC, an umbrella organisation representing 13 leading UK aid agencies.
It is the first time in the DEC's 45-year history that donations rose rather than fell during the second week of an appeal.
Donations to the Haiti Earthquake Appeal dropped by 28% in the second week of the appeal, those to the Indonesia, Philippines and Vietnam Appeal fell 62%, Burma donations dropped by 54% and for the Tsunami the second week fall was 24%.
Donations to the Pakistan Floods Appeal, which was launched on August 5, increased by 18% in the second week and have not yet started dropping.
Mr Gormley said: "This is a tragedy unfolding in slow motion with new areas still being flooded and the threat of deadly waterborne disasters stalking millions of survivors. The full impact of the disaster will only be revealed when flood waters finally recede and the extent of devastation is uncovered."
The current death toll was said to have risen to 1,600 but Jane Cocking, humanitarian director of Oxfam, said it could rise sharply if there is a significant outbreak of waterborne disease and those affected are unable to get swift medical care.