Our forces are performing daily acts of heroism in the toughest of combat environments. The amount of ammunition used testifies to the ferocity of the fighting. Forty-five soldiers have been killed in action. And yet several soldiers I spoke to felt they were taking part in a forgotten campaign.

We need to wake up to what is happening in Afghanistan. As the cradle of 9/11, preventing a relapse into Taliban control matters fundamentally to Britain's national security.

Due to the campaign over the past year, the military position has shifted away from the Taliban. In a conventional military sense, the insurgents are on the back foot. And yet our commanders are the first to say that military force alone will not bring stability. If we carry on as we are we could end up winning the war in Afghanistan, but still lose the country.

A year ago, General David Richards, then the British Commander of Nato's International Security Assistance Force (Isaf), warned of the risk of failing in Afghanistan. To avoid this we now need to make some urgent course corrections. First, we must be realistic about what we are aiming to achieve, and the timescale. As our ambassador has said, this is a marathon, not a sprint. We need to avoid giving the impression that we can impose fully fledged Western notions of democracy and liberalism in a society that is deeply traditional. We must work with the grain of Afghan society.

Second, we need to promote local security solutions. Up to now, it has been too easy, once international forces have left an area, for the Taliban to slip back in. We need to give overriding priority to training up the Afghan army, as well as the police, whose reputation - in contrast to the army - is patchy. We should also look at how we can persuade shuras and tribal elders to help shore up local security.

Third, we need to change the way the international effort is run. It maximises confusion and duplication. It lacks the most basic pre-requisites essential in counter-insurgency and stabilisation operations: unity of purpose and unity of command.

On the military side, there are no fewer than seven chains of command. Isaf and the US-led Operation Enduring Freedom operate in parallel, one focusing on long-term peace and stability, the other on al-Qa'ida and terrorist networks. There is a strong case for merging the two, or dual-hatting Isaf's commander.

Nato, for its part, needs to raise its game. It is too bureaucratic and unwieldy. The lack of helicopters is constraining operations. If Nato cannot provide more helicopters - astonishing, given the hundreds which allies have on paper - then why can Nato not contract helicopters for ferrying cargo, and free up military helicopters for urgent frontline tasks?

Things are no better on the civilian side. There are at least 100 agencies in Afghanistan with more than $100m (£50m) to spend. No one has the authority to co-ordinate this sprawling effort. The time has come to appoint a senior, high-profile individual to provide leadership, much as Paddy Ashdown did successfully in Bosnia and Herzegovina. I raised this idea in Kabul a year ago: the need for such an appointment is now acute. That individual should have the authority of key capitals, as well as the UN and EU, to co-ordinate the effort on the ground.

Finally, we should look at extending the tours of our senior commanders to allow them to use to the full the contacts they make with tribal leaders and Afghan army officers. Any such change would have to be accompanied by alterations to welfare arrangements. Conversely, there may be a case for reducing the tours for fighting troops to four rather than six months - moving closer to the rotational model which we employed successfully in Northern Ireland.

Here at home, people are entitled to a clearer understanding of the Government's commitment in Afghanistan. The scale of the mission is daunting, and it is set to last many years. We must avoid repeating in Afghanistan the mistakes of Iraq. Foremost amongst these was the absence of a proper plan. It is still not evident that we have a proper plan in Afghanistan.

For the sake of our forces who are performing magnificently, for the sake of Britain's security, for the sake of Afghanistan and its neighbours, Gordon Brown needs to level with the public about the challenges we face, and put in place a plan to meet them.

The writer is Leader of the Opposition