British Prime Minister David Cameron has warned Pakistan not to have any relationship with groups that "promote the export of terror".
He said that he would be raising the issue with his Indian counterpart Manmohan Singh when they held talks in Delhi on Thursday.
Mr Cameron's spokeswoman insisted he was talking about Pakistan as a country, not its government.
She said that the main message was for Pakistan to shut "terror groups" down.
"We should be very, very clear with Pakistan that we want to see a strong, stable and democratic Pakistan," Mr Cameron told reporters after a speech in the southern Indian city of 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."
His remarks on Pakistan follow the leaking of US documents on the WikiLeaks website in which Pakistan's Inter Services Intelligence agency was accused of secretly helping the Afghan insurgency.
UK Foreign Secretary William Hague, who is travelling with the prime minister, sought to further clarify Mr Cameron's remarks.
"He wasn't accusing anybody of double dealing," Mr Hague said.
"He was also saying that Pakistan's made great progress in tackling terrorism. Of course there have been many terrorism outrages in Pakistan itself."
The BBC's world affairs correspondent Mike Wooldridge says that the leaking of this particular allegation has already been the cue for increased American demands that Pakistan needs to step up its efforts to tackle terrorism and Mr Cameron is saying the same.
Our correspondent says that Mr Cameron and his officials also put great emphasis on the importance of Britain and Pakistan working together to make the country stronger and more stable.
"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," Mr Cameron 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."
His comments are likely to be welcomed by officials in Delhi, which has long accused its neighbour of backing attacks on Indian targets.
The two nuclear-armed rivals have fought three wars, with peace negotiations stalling following the Mumbai attacks of 2008, which India blamed on Pakistani-based militants.