Half of the major terrorist plots threatening Britain emerge from Afghanistan and Pakistan nearly 11 years after UK troops joined a US-led coalition to oust the Taliban, David Cameron said today.
But the Prime Minister added the number of terror plans hatched in the two countries had dropped in recent years.
He said: "Britain has played a leading role in this alliance for reasons of our own national security.
"Three years ago some three quarters of the most serious terrorist plots against Britain had links to Afghanistan and Pakistan.
"I'm now advised that figure has fallen to around a half."
Mr Cameron was speaking as he updated the Commons on last weekend's Nato summit in Chicago where he confirmed British troops - like other international forces - will end their combat role in Afghanistan by the end of 2014.
Labour leader Ed Miliband backed the withdrawal plan but demanded quicker action on peace talks between the Afghan government and the Taliban.
A total of 414 British servicemen and women have been killed in Afghanistan since the start of operations against the ruling Taliban and al-Qaida terrorists in October 2001 following the previous month's attacks in the US.
The PM said attacks from Afghan insurgents had fallen recently and the handover of swathes of the country to Afghan security forces was going as planned with nearly 75% of the population living in areas controlled by Afghan policemen and soldiers.
But he called on other Nato nations to fund bolstering Afghan security forces and hailed the 1 billion dollars pledged at the summit to back the regime.
He added: "Our aim is an Afghanistan that is able to take care of its own security without the need for foreign troops, an Afghanistan that can prevent al-Qaida returning and posing a threat to us and our allies around the world.
"The tremendous hard work of our courageous servicemen and women is making this possible and, after 10 long years, our servicemen and women will finally be coming home."
Mr Miliband demanded "concrete steps for an inclusive a political settlement", adding: "The international community has been talking for a long time about talks about talks in relation to the political settlement we need, and we need far greater urgency in seeking this settlement to be there for when our troops come home."