Afghans must be free to set laws that clash with western values and legal principles if order is to be established in the country, Des Browne, the UK defence secretary, said yesterday.

In an address to the Brookings Institution in Washington, Mr Browne said policymakers must drop any illusions of "imposing a Jeffersonian democracy" and press forward with "Afghanisation" of the justice and police systems. This would mean, where necessary, supporting laws and structures that "may not sit easily with our culture and norms but do so with theirs", he said.

"We, the international community, need to have an honest debate about the type of legal system that a country called the 'Islamic Republic of Afghanistan' needs," he said. "A western model would be inappropriate and unsustainable."

Mr Browne's speech is intended to offer some UK input into a wide-ranging policy review under way in Washington. He will meet Robert Gates, US defence secretary, during his visit.

Officials in Washington say that the review, which the Bush administration hopes to conclude soon, is intended to thrash out a more coherent approach to the south of Afghanistan, with a particular focus on civil-military co-ordination.

It comes amid a rise in violence in Afghanistan - where more US soldiers die monthly than in Iraq - and criticism from US senators and independent think-tanks of international strategy.

While Nato forces have the goal of bolstering the authority of the Karzai government throughout the country, US officials admit that, in fact, it has little influence in parts of the south. They add that Nato, US forces and civilian aid donors should be better co-ordinated in the area. Washington has also struggled to deal with cross-border incursions from Pakistan and the booming drug business in the south, which partly finances the Taliban.

Sean McCormack, US State department spokesman, said the US was at an "advanced stage" of the review it was carrying out with its partners on southern Afghanistan. He added that the review would "provide the next [US] administration a firm foundation on which they can build on the US's continuing partnership with Afghanistan".

Unless Afghans were given the support to build a justice system that fitted their own culture and the nation's infrastructure, efforts to create an effective police force would continue to be undermined, Mr Browne warned.

While pro-gress has been made in training the Afghan army, the police are re-garded as "corrupt", he said.