The main opposition parties have given cautious support to a widening of the military campaign following the defeat of the Taliban but are warning the West cannot walk away from Afghanistan.

The Conservatives and Liberal Democrats have called on the government to ensure it achieves its aims in Afghanistan and help establish the new government before considering widening the campaign to include countries with terrorist links.

Following the fall of the Taliban stronghold of Kandahar calls have already been made for military strikes to be made against Iraq and the Sudan.

Bernard Jenkin, the shadow defence secretary, said peacekeeping efforts would have to be put in place to ensure the long-term survival of the fledgling Afghan government.

"We hope that the interim administration will be established and that other nations contribute to the necessary peace keeping and that the West will take a long term interest in the future of Afghanistan," he said.

He said the core objective in the response to the US terrorist attacks was the defeat of the Al Qaeda network which would not end with the capture of Osama Bin Laden.

"The objectives of the campaign against terror have always been about much more than just Afghanistan. Al Qaeda exists in other countries and we must help host governments to eliminate Al Qaeda. Governments that deliberately harbour terrorists are no better than the terrorists themselves. Both the US and UK support this view," he said.

Liberal Democrat defence spokesman, Paul Keetch, said it was vital that the allies helped the new government of Afghanistan to rebuild its shattered economy and infrastructure.

"We said we would not walk away this time and we need to ensure that the US, Britain and the other countries honour that pledge," he said. "The allies need to conclude operations in Afghanistan before we consider what happens next. With the Taliban now surrendering one of the principle war aims is still not yet achieved - bringing Bin Laden to justice."

Keetch said any widening of the campaign had to be pre-empted by the same diplomatic efforts and UN resolution that were in place before the war in Afghanistan.

"We would be very unhappy supporting military action against another country unless there is clear evidence of involvement in the US terrorist attacks or they are shielding people involved in them. There was international support for the military action in Afghanistan, as expressed at the UN and we would need a similar agreement for any further action," he said.