Bangalore: British Prime Minister said on Wednesday that Pakistan must stop becoming a base for militants and not "promote the export of terror" across the globe.
David Cameron's remarks, made during a visit to Pakistan's arch rival India, are likely to give cheer to officials in Delhi, who have long accused their neighbour of backing attacks on Indian targets.
The two nuclear-armed rivals have fought three wars, and a faltering peace process, which completely stalled after militant attacks in Mumbai in 2008, remains deadlocked.
"We should be very, very clear with Pakistan that we want to see a strong, stable and democratic Pakistan," Cameron told reporters after a speech in Bangalore.
"We cannot tolerate in any sense the idea that this country is allowed to look both ways and is able, in any way, to promote the export of terror, whether to India or whether to Afghanistan or anywhere else in the world," he added.
Cameron's remarks come days after classified US military reports published on the whistle-blower WikiLeaks website detail the US concern that Pakistan secretly aided Taliban militants while taking billions of dollars in US aid.
Pakistan is seen as key to any negotiations to end the nine-year-old war in Afghanistan because of its influence over the Taliban.
Analysts believe the leadership council of the Afghan Taliban is hiding in Pakistan.
Britain is home to a large minority of people of Pakistani-origin and Cameron stressed the importance of Britain's relationship with the Muslim country.
"It should be a relationship based on a very clear message: that it is not right to have any relationship with groups that are promoting terror," he said.
"Democratic states that want to be part of the developed world cannot do that. The message to Pakistan from the US and the UK is very clear on that point."
Britain has 9,500 troops fighting in Afghanistan and a rising death toll there is making the campaign increasingly unpopular. Britain justifies the war by saying the majority of terrorist plots uncovered here have their roots in the lawless Afghan-Pakistan border areas.