PM pledges cash to fight terrorism
Extra money will be available to fight "troubling" security threats to Northern Ireland, the Prime Minister has promised.
A third of the Police Service of Northern Ireland's budget goes on combating the terror danger, with a string of recent bomb attacks by dissident republicans.
Last month the Real IRA said it planted a device which damaged a bank and shops in Londonderry.
Mr Cameron said: "We are standing by the commitments made by the former Prime Minister. We believe we are meeting those. This is something we have to keep under review. There was agreed access to the (money) reserve as proposed by the former Prime Minister, we stick to that."
Policing and justice powers were devolved from Westminster to the Northern Ireland Assembly earlier this year.
The Tory leader added: "Having devolved policing and justice it is very important that we say to colleagues in Northern Ireland that you must try to make the best you can with that. We should not try to stand on their shoulders the whole time."
Mr Cameron said the Government was honouring commitments by the former Prime Minister on funding the creation of a policing college near Cookstown, Co Tyrone.
He added security issues in Northern Ireland had been discussed by the National Security Council. "The security situation is troubling," he said.
There have been several attacks in recent months blamed on dissident republicans.
Home Secretary Theresa May is among those warning of the heightened risk.