Archbishop Desmond Tutu and other leaders are calling on the world to give “more quickly and generously” to help millions of people affected by floods in Pakistan.

The Elders, a group of distinguished independent leaders, warned that the situation in Pakistan was deteriorating rapidly and that little aid was reaching many of those affected.

Some 3.5 million people are now at risk of water-borne illness such as hepatitis and diarrhoea. The Elders said the scale of the flooding was “disastrous” and that its long-term impact would be felt by around 20 million people.

Tutu appealed to governments and individuals to give as generously as they did in the aftermath of the 2004 Boxing Day tsunami and the massive earthquake that struck Haiti in January.

“I urge people all around the world to hold the people of Pakistan in their hearts and in the heart of the human family at this time,” he said.

“Let us not for a moment allow ourselves to feel that some are less deserving of our help than others.

“It is time for us to stand in solidarity with the people of Pakistan. Please give generously and help to share their enormous burden as they struggle to recover.”

The call for more donations comes as the United Nations General Assembly meets today to discuss Pakistan’s humanitarian emergency.

It has launched a $460 million emergency appeal but so far only half of that amount has been pledged, with aid agencies warning that the amount of money that has come in so far will not last more than three months.

The Disasters Emergency Committee said £24 million people had been raised by the British public so far, enabling its members, including Christian Aid and World Vision, to reach over 700,000 people.

DEC Chief Executive Brendan Gormley said the public had “understood that this crisis is still growing in scale and requires ongoing support to make a real difference to the millions affected”.

“With a fifth of Pakistan under water, aid agencies continue to work around the clock to reach those in need of immediate humanitarian assistance. And with the risk of diseases like cholera and malaria growing by the day, it is vital that people keep giving,” he said.

An estimated 1,600 people have died in the floods, while hundreds of thousands have lost their homes, and crops, livestock and communication networks have been destroyed.