In a series of developments which showed that the war in Afghanistan was in danger of slipping into diplomatic and military chaos, Geoff Hoon, the Secretary of State for Defence, told The Observer that the situation on the ground was 'pretty grim' and that a contingent of 6,000 British troops may now not be deployed in Kabul.

As fighting continued throughout parts of the country still under the Taliban's control, Hoon also indicated that the group of 100 troops, including members of the Special Boat Squadron, already in the capital could be pulled out as tribal warlords began carving up the country, demanding bribes from locals, killing captured Taliban soldiers and looting property from civilians.

'It sounds pretty dangerous,' Hoon said in an interview with The Observer . 'If they have completed their work we will pull them out. We are not keeping them there for the sake of it.

'If they say we have got enough information, they will come out and we will then make a judgment as to who goes in, if anyone goes in, thereafter.'

The Northern Alliance warlords, competing for supremacy as the country drifts into a political vacuum, said that the British forces had never been invited and that they would not allow a large force in to secure the key airstrip at Bagram on the outskirts of the capital.

Mines litter the area and there are fears that marauding militias, hardened by years of conflict, could inflict serious casualties on any large-scale British force. Special forces were also said to be in the mountains carrying out search-and-destroy missions on al-Qaeda troops.

Yesterday Engineer Arif, the Alliance's deputy intelligence chief and a senior figure in the organisation, said that the troops had arrived without proper consultation and that only 15 could stay to undertake 'humanitarian tasks'.

Hours later Dr Abdullah Abdullah, the Alliance's Foreign Minister, said that there was no agreement on enlarging the force.

'We are talking about a number less than one hundred British soldiers,' he said. 'If we are talking about the presence of thousands of fighting forces from outside Afghanistan then this is an issue that must be discussed.'

The news comes as a significant blow to efforts to put humanitarian systems in place before the snows of winter set in. Without an operating airfield, large drops of food or peace-keeping forces will not be possible. The chaos also raises the spectre of the country once more being plunged into anarchy by tribal warlords, who now no longer need allied help to drive out the Taliban.

Hoon said British troops would not be put in danger, suggesting that a major reassessment of military options in Afghanistan was taking place.

It now seems clear that plans to put a large contingent of British troops on the ground in Afghanistan have been put on hold. Sources said that any deployment was not imminent.

The arrival in Afghanistan of the Government's special envoy, Stephen Evans, has also been delayed.

'It has to be dependent on the situation on the ground, how that evolves and crucially whether we can get them [British troops] in safely,' Hoon said. 'We are certainly not going to put them in and take risks with them.'

Military sources said that individuals who had set their face against the arrival of coalition forces could wreak havoc.

'You have to bear in mind that a single Taliban with a shoulder-launched missile, hiding not too far off that runway, could cause a massive problem,' an official closely linked to the British military campaign said.

'One C130 [supply plane] coming down as a result of being hit, a slow-moving aircraft hit by a missile as it is coming in or taking off, you would lose a lot of people.'

Yesterday the former Afghan president, Burhanuddin Rabbani, arrived in the newly captured capital for the first time since he was driven out by the Taliban in 1996.

It is feared that this could mark a return to the factional fighting that destroyed the country after 1992, when rival warlords carved the country into personal fiefdoms and paved the way for the Taliban's rise to power. Rabbani insisted that he wanted to see a broadly based government as demanded by the Americans and the British but officials in the area suggested he would not agree to United Nations demands that the first conference of Afghan leaders be held in a neutral venue.

It appears that Rabbani will demand it is held in Kabul and will make it clear that the Northern Alliance is negotiating from a position of strength.

In a move to try to stave off any faction fighting, the UN envoy, Francesc Vendrell, arrived in the capital yesterday to try to help work out a plan for a new Afghan government.

It was also unclear last night whether Osama bin Laden was still in the country. The Taliban envoy to Pakistan, Abdul Salam Zaeef, said bin Laden had left Afghanistan and the Islamic militia did not know his whereabouts.

'Osama has left Afghanistan with his children and his wives and we have no idea where he has gone,' Zaeef said.