Defence Secretary Philip Hammond has insisted Government policy in Afghanistan remains unchanged despite an announcement that Nato forces are scaling back joint operations with Afghan forces.

Mr Hammond welcomed the news, saying he wanted to do everything possible to protect British troops from the wave of "green-on-blue" attacks which have seen 51 international troops killed this year by Afghan forces or militants wearing their uniforms.

But he insisted that the announcement by the International Security Assistance Force (ISAF) was only a "draft order" and would have "minimal" impact on operations by UK forces in Afghanistan.

Mr Hammond was coming under pressure to come to the House of Commons to answer questions on a development which one MP said marked a complete reversal of US and UK strategy in Afghanistan, under which international troops will stay until the end of 2014 to train and mentor home-grown security forces.

The Defence Secretary insisted this strategy had not changed, telling reporters: "We have got a strategic plan. We are working towards an end to our combat operations in 2014."

Isaf announced in a statement overnight that most joint patrols and advisory work with Afghan troops will now only be conducted at the battalion level and above, while co-operation with smaller units will have to be "evaluated on a case-by-case basis and approved by RC (regional) commanders". Isaf insisted in its statement that it remained committed to its partnership with the Afghan National Security Forces (ANSF).

Labour MP Denis MacShane sought to force Mr Hammond to come to the Commons to answer an urgent question on the announcement. The Defence Secretary appeared before MPs on Monday to answer an urgent question from Dr MacShane, but made no mention of any change in joint working with Afghan troops.

The Rotherham MP suggested that he believed Mr Hammond had simply not been informed by the Pentagon of the impending shift in procedures, and described it as a "humiliation" for the Defence Secretary. Shadow defence secretary Douglas Alexander said that Mr Hammond needed to explain whether the announcement represents "a temporary tactical response by military commanders on the ground or... a more strategic shift in the mission".

Taliban sources claimed Bastion was targeted because Prince Harry is serving there as an Apache attack helicopter gunner, but Mr Hammond revealed that the Prince was moved to a guarded location during the attack.

Answering an urgent question in the Commons, Mr Hammond insisted the strategy of "mentoring and training" Afghan army and police was vital to the war effort, adding: "We cannot and we will not allow the process to be derailed."