Afghanistan is "not a failing mission" and British troops have brought real change to people's lives in that country, the defence secretary has said.
Des Browne attacked the Conservatives and the media for their criticism of the effort in which 40 British soldiers have died, 33 of them since they began operations in the south of the country in May.
He said that people were entitled to their views, but warned: "Let's take responsibility for the way we discuss these things and not do it in a way which puts our people, the people we send to do this hard, dirty and dangerous work on our behalf, at risk."
"We always knew the south would be more difficult - it is the heartland of the Taliban and it has been lawless for decades," Mr Browne told the Labour party conference in Manchester.
He added: "But we have to tackle Helmand and the south - and eventually the east - if we are to secure what we've already achieved in the rest of Afghanistan."
The defence secretary refuted Tory claims that troops were "confused" about their role - although originally intended to help the Kabul government enforce power in the south, British soldiers have come up against increasingly violent opposition.
"Talk to the soldiers themselves - they are not confused about what they are doing. Yes they are there to rebuild, but they cannot rebuild without first creating security," he said.
"And that means fighting what is necessary - fighting the Taliban and the drug lords who will do anything to prevent us creating security."
This weekend leaked emails from a British army major serving in Afghanistan added to the mounting concerns that troops there were ill-prepared for the situation they have found themselves in.
Major James Loden of 3 Para described the RAF as "utterly, utterly useless" at protecting troops on the ground and said more manpower and helicopters were "desperately" needed.
But today Mr Browne insisted that the Tories' attempts to persuade the public and the soldiers themselves "that we are not fully supporting them, either because as a party we don't 'get' defence' or because we don't want to pay for it", were wrong.
"In fact the opposite is true - every time we have gone to the Treasury for more money to support and protect our troops we have got it," he said, citing the £70 million provided in July for new armoured vehicles in Iraq and Afghanistan.
The defence secretary's focus on Afghanistan reveals the increasing concern about the military operation there - he reserved just one paragraph for Iraq.
There, he said the coalition's aim was "trying to get the country to a point where we can bring our forces home without it slipping into civil war".