The Prime Minister was criticised for offering to spend more than £600 million of British taxpayers’ money in a country whose government he admitted could waste at least some of the aid.
Visiting Islamabad, the Pakistani capital, Mr Cameron announced that over the next four years, British aid for education in Pakistan could reach £650 million.
Britain’s last four-year budget, from 2009-13, allocated £250 million for education.
The major increase in school aid could lead to four million Pakistani children attending school for the first time, officials said. It would also make the country the biggest single recipient from Britain’s growing aid budget.
Despite protests from some Conservative MPs, Mr Cameron is increasing aid spending, even as other departments see their budgets cut.
Pakistan spent barely 2 per cent of its annual budget on education, but more than 15 per cent went on defence.
Britain is cutting its defence budget by 8 per cent, cutting 17,000 military posts and scrapping warships and fighter jets.
By contrast, Islamabad is in talks with China to buy six submarines at a potential cost of more than £1 billion.
The Pakistani government may also spend another £1 billion on Chinese fighter aircraft.
Mr Cameron insisted that the support for education in Pakistan was in Britain’s long-term interests because illiteracy and poor schooling were a “root cause” of Islamic extremism and terrorism. But he conceded that the move would be controversial, and admitted that corruption and waste in Pakistan made it harder to justify British aid payments.
“The British people want to know every penny we do spend is going to the right places,” he said in a speech at a university in Islamabad.
“I need to convince them that it is. But my job is made more difficult when people in Britain look at Pakistan, a country that receives millions of pounds of our aid money, and see weakness in terms of government capacity and waste.”
Mr Cameron said the answer was for Pakistan to tighten its tax code, ensuring more people paid more tax.
Many of Pakistan’s richest people “are getting away without paying much tax at all. That’s not fair,” he said.
Privately, even British diplomats were uncomfortable about the large increase in aid to Pakistan because of widespread fears that government corruption would prevent at least some of the money reaching its intended destination.
Philip Davies, a Conservative MP, said cuts in British public services made it impossible to justify increased aid payments.
“That is especially the case with countries that can afford to spend billions of pounds on defence,” he said. “If they can afford submarines they can afford to educate their own people.”
As part of a new “security dialogue”, Mr Cameron announced that Britain would join the US in funding a Pakistan “centre of excellence” to develop bomb-disposal techniques.
That could mean sharing sensitive military secrets with the country’s intelligence agencies, which had been accused of supporting militant groups, including the Taliban in Afghanistan.
The Prime Minister insisted that helping Pakistan would make Britain safer.
“I would struggle to find a country that is more in our interests to see succeed than Pakistan,” he said.
“If we fail, we will have all the problems of migration, of extremism — problems that we don’t want to see.”