Nick Clegg warned today that flood-hit Pakistan will need aid for years to come as he saw the devastation for himself.
The Deputy Prime Minister said the disaster would have a "long tail", with threats from water-borne disease and opportunistic extremists.
Speaking after being shown aid camps near the southern town of Sukkur - one of the worst affected regions - Mr Clegg said: "I think the sheer scale of this, it is really quite difficult to comprehend.
"The terrible thing is that it has got a long tail. It has got a lot of aftershocks that are going to last for a long time."
He said the international community's response has been too slow, but praised donations from the British Government and public.
"We have to make a huge effort to provide important emergency aid, but really stick with this for the long term," he said.
Mr Clegg stressed that the flood waters have not drained away in many areas, and there is a "real danger of diseases taking hold".
"It's going to take years and years for normality to come back to Pakistan," he added.
He also warned that the influence of extremist groups could be boosted by the disaster.
"The danger always is that you get groups who have an ulterior motive who provide aid to try to curry favour," he went on.
The Deputy Prime Minister toured the Pakistan Air Force flood relief camp at Sukkur, which houses more than 3,000 refugees. He was shown a clinic and chatted with children at a makeshift school, before moving on to the UN World Food Programme distribution base.
At nearby Sukkur airport he received a briefing from aid agencies and met President Asif Ali Zardari, who was also touring the disaster scene.
Mr Clegg discussed the situation with the president, and briefed him on his visit to Afghanistan and talks with President Hamid Karzai yesterday.
More details of how the Government's £33 million of aid will be allocated were released to coincide with Mr Clegg's visit.
About £9 million is going on items to help the millions displaced, including:
:: 2,330 water pumps for safe drinking supplies;
:: Emergency shelter kits for around 30,500 families;
:: Repairing or installing 5,000 toilets;
:: Spades, picks and wheelbarrows to help 1,600 families clear debris from their homes;
:: 650 kits containing essentials for newborn babies.
The money will be given to charities Save The Children, Concern and Oxfam to source and distribute supplies.
The aid will be targeted at the Punjab and Sindh provinces where the floods have had the worst impact.Reuse content