At a meeting of Nato's parliamentary assembly in Edinburgh, Scotland on Tuesday, David Miliband said that history suggested many Taliban members could be persuaded to stop fighting.
Miliband said the Afghan government would need to reach out to "high-level commanders that can be persuaded to renounce al-Qaeda and pursue their goals peacefully".
"This will be far from straightforward. But the historical lessons are clear," he said.
"Blood enemies from the Soviet period and the civil war now work together in government. Former Talibs already sit in the parliament.
"It is essential that, when the time is right, members of the current insurgency are
encouraged to follow suit," he said.
Marwan Bishara, Al Jazeera's senior political analyst, said there was nothing new about Miliband's proposal.
"It's kind of funny hearing foreign secretary Miliband speaking of this as if it is all new invention," he said.
"In fact, this has been tried since the 1950s. There's no counterinsurgency without a political programme.
"At the heart of it is winning the population. In fact, scaring the population into playing ball, if you will, with the occupier."
Miliband's comments came shortly after Anders Fogh Rasmussen, Nato secretary-general, said he expected the military alliance's member nations to pledge "substantially more forces" to Afghanistan.
He said he expected the alliance to decide on "a counter-insurgency approach, with substantially more forces" in the coming weeks.
"We can, and should, start next year to hand over more lead responsibility for security to Afghan forces.
"We will do this in a co-ordinated way, where conditions permit, and this will allow us to progressively move into a support role."
His comments reflected proposals by Gordon Brown, Britain's prime minister, who suggested on Monday that a timeframe for handing over security district by district could be drawn up in the new year.