On the final day of Labour’s gathering on the Sussex coast, the Foreign Secretary made clear the UK Government would not be risking the lives of British soldiers, if ministers were not convinced the work they were doing was essential to security in Britain.

If the coalition were to abandon its work there, he warned: “The clock would be turned back to the 1990s, when Afghanistan was a place for al Qaeda to seduce, groom, train and plan for deadly terrorist missions. With the best of intentions, withdrawal would mean risking the next 9/11 or 7/7.

“We will wait to get a credible election result and we will not be rushed into a whitewash,” he insisted.

Earlier, Bob Ainsworth said he was unable to put a time limit on Britain’s deployment in Afghanistan but gave the assurance that there would be no increase in UK troop numbers unless they were properly equipped.

The Defence Secretary told delegates: “We can’t afford not to be there. For Britain to be secure, Afghanistan needs to be secure, Pakistan needs to be secure.”

He went on: “The threat may be less visible but it is no less real. The risks of leaving Afghanistan before the job is finished are stark.”

Mr Ainsworth acknowledged there were “difficult decisions” to be taken about sending more troops to Afghanistan. “We will take those decisions as an alliance, although the UK cannot allow the deployment of its troops to outstrip the supply of equipment that allows them to do their job and minimises the risks they face.

“Before I agree to any increase in troop numbers, I must be sure that the balance of risk is acceptable by evaluating the capacity of the supply chain to properly equip the increased force.”

He conceded the Afghan elections “were not everything we had hoped” amid widespread allegations of corruption and vote rigging.

However, he stressed that the ballot taking place at all in the face of Taliban attacks had been an achievement.

Elsewhere, Gordon Brown said the Taliban would “easily take back control of Afghanistan, if we were not there”.

The Prime Minister said: “We are protecting the streets of Britain as well as protecting the security of Afghanistan but the strategy has had to change.

“We have got to be part of a group of countries that are bringing Afghan people back into control of the army, the police, local government and, of course, we cannot make final decisions about what we do next until we know the election results.”