Cameron's remarks that Pakistan must not be allowed to "look both ways" have fuelled a diplomatic row, with an angry Pakistan stating the remarks could damage the prospects for regional peace.
Cameron, currently on a visit to India, had delivered a tough message to Pakistan, asking it to stop promoting any "export of terror" to India or anywhere else, and had stated that the country should not be allowed to "look both ways".
A Pakistani official said in Islamabad last night that in combating terrorism, Pakistan had done more than any other nation.
However, an unperturbed Cameron today said the facts have to be stated as they were, and made it clear that he did not intend to retract his comments.
The Prime Minister reiterated that more needs to be done on the terror front in Pakistan.
"I think you should say what you think, and be frank and clear," Cameron told Sky news.
"It's not acceptable that there are still terrorist groups working in Pakistan. We need to work with the government there to shut them down. There is action being taken, but we need to see more," he said.
Cameron's repeated warning to Pakistan came after Islamabad had made its displeasure clear over the prime minister's remarks.
Foreign Office spokesperson Abdul Basit said last night that Pakistanis had rendered innumerable sacrifices in the fight against terror.
"We hope that our friends will be able to persuade India to view this issue objectively and the value of 'cooperation' in counter-terrorism," Basit said in a reaction to Cameron's remarks in India.
Pakistan's high commissioner to Britain, Wajid Shamsul Hasan, in a comment in the Guardian newspaper wrote that people in Pakistan were "really hurt" by Cameron's remarks and called on him to "make amends".