BASHAR Assad's regime in Syria is deliberately using the denial of humanitarian aid as a political and military weapon, the UK Government has claimed, as it came under pressure from the SNP to drop “bread not bombs” on starving civilians.

David Lidington, the Foreign Office minister, said international pressure - including the possibility of air drops - had led to the Syrian government agreeing in principle to allow the United Nations to deliver aid by land routes to the majority of requested areas in June.

But he added that Assad's regime must be held to account to ensure besieged citizens received the aid they needed and called on Iran and Russia to use their influence over the government in Damascus.

In an Urgent Question in the Commons, Labour’s Diana Johnson, said there was now a clear humanitarian crisis in Syria with 582,000 people living in besieged areas.

"The conditions for the men, women and children in these areas is beyond what many of us can comprehend and in the words of the UK's special envoy to the UN 'it's a concept from medieval times; starvation as a weapon of war and purposefully withholding life-saving medicine'. Yet this is what the Assad regime is doing."

MPs heard that limited aid had reached parts of Syria with Ms Johnson noting this had not always included food and that "children are still starving".

The Labour frontbencher noted that while Foreign Secretary Philip Hammond had made clear the International Syria Support Group would commence air drops into besieged areas if aid was not allowed in by June 1, the UN was briefing that it had made a request to the Syrian government to commence airlifts not air drops, meaning it now appeared aid would only arrive at the whim of the Assad regime.

Mr Lidington replied that no one “should be under any illusions that they[the Assad regime] are deliberately using the denial of access to humanitarian aid as a political and military weapon".

He said the UN should lead talks with the Assad regime and the delivery of humanitarian aid, adding that the best outcome would be agreed terms of access either via land or by air for World Food Programme assistance.

"That would be better than other powers trying to intervene," insisted Mr Lidington.

But the SNP’s Tasmina Ahmed-Sheikh said the UK had an "absolute moral responsibility to protect civilians" in Syria as she asked: "Is it really the case that we are asking for permission from Assad to feed the very people he himself has starved?"

Mr Lidington replied: "It is the United Nations that is talking to the Assad regime about getting access. It is the United Nations that has the good offices to make those approaches and the United Nations which is in charge of delivering the humanitarian assistance.”

He added: "That is the way forward that we judge at the moment is most likely to lead to a successful outcome and one that is safe both for those receiving the aid and for those delivering it."

But later, Ms Ahmed-Sheik, who represents Ochil and South Perthshire, said: “Over 500,000 people are living under siege in Syria today and there are some towns which have not received food aid since 2012.

“We have a moral responsibility to protect civilians who are suffering from the wider effects of a conflict in which the UK is now an active participant.

“No expense has been spared in dropping the UK’s hi-tech missiles on the country but it is bread not bombs that people in Syria need now,” she declared.