THE SNP has demanded a halt to the sale of UK weapons to Saudi Arabia amid growing concern they are killing thousands of civilians in the war-torn gulf state of Yemen.

Westminster leader Angus Robertson last night called on David Cameron to block sales after claims the UK Government is breaking national, EU and international law by supplying weapons to a Saudi-led bombing campaign in Yemen.

In a letter to Cameron, Robertson requested an urgent meeting to discuss the situation.

Last month a legal opinion commissioned by Amnesty International and the Saferworld NGO concluded the UK was breaching its obligations under the UK’s Consolidated Criteria on arms exports, the EU Common Position on Arms Exports and the Arms Trade Treaty by supplying weapons to Saudi Arabia capable of use in Yemen.

A Saudi-led coalition began bombing Yemen in March 2015 after the government was overthrown by rebels sponsored by the Kingdom's main regional rival, Iran.

Since then an estimated 2,800 civilians have died in a civil war dubbed “Saudi Arabia’s Vietnam”, with accusations that the coalition has used cluster bombs in populated areas.

The UK has also issued more than 100 licences for arms exports to Saudi Arabia - more than £1.75bn worth in the first half of 2015 alone - most of which appear to be for combat aircraft and bombs for the Royal Saudi Air Force, whose pilots are trained by British instructors.

Since 2010, the UK has licensed a total of £5.6bn of arms sales to Saudi Arabia, including fighter jets, tear gas, military vehicles and targeting equipment.

Robertson last week challenged Cameron on the issue at Prime Minister’s Questions, attacking him for allowing British weaponry and British military advisers to become an integral part of the war in Yemen without parliament's approval.

Robertson told the Sunday Herald: “The UK is effectively at war, and is potentially involved in the loss of thousands of civilian lives, yet the Prime Minister has swept it under the carpet. The lack of transparency has been alarming.

“World attention on conflict in the Middle East is focussed on Syria and Iraq and sadly the catastrophic war in Yemen is largely overlooked.”

Robertson said he also wanted the Commons Committee on Arms Exports Controls, which has not been reconvened since the general election, re-instated immediately to scrutinise the matter.

"The public have a right to know if British-built bombs are responsible for civilian deaths."

Naomi McAuliffe, Amnesty International’s Programme Director in Scotland, welcomed the SNP's call.

She said: “Angus Robertson has raised an important point about the UK’s involvement in Saudi Arabia’s indiscriminate bombing campaign in Yemen.

“It is absolutely unacceptable that the UK government granted over £1bn worth of arms export licences for Saudi Arabia in just three months last year.

“There is overwhelming evidence that weapons sold by the UK are being used to destroy Yemeni homes, schools and hospitals, with a continuing risk of civilian deaths.

"The prime minister should immediately suspend export licences for all further UK arms bound for Saudi Arabia and allow a full investigation into allegations of serious breaches of international humanitarian law by Saudi Arabia in Yemen.”

Paul Murphy, executive director of Saferworld, added: "UK Government policy on Yemen is in disarray. The UK gives aid to Yemen with one hand while supporting the destruction of the country with the other. It’s time the UK acted as a peace broker, rather than an arms broker. The UK government must halt these arms sales immediately.”

Robertson was accused of hypocrisy after his PMQs intervention, when it emerged he had signed a Commons early day motion in 2012 calling on UK ministers to ensure the then Yemeni President had “all the security equipment and training assistance his forces require”.

A Downing Street insider said: "The Prime Minister gave clear answers to Mr Robertson on Wednesday. And as we now know, the SNP Westminster Leader is all over the place on the issue. One day he signs a motion calling for action, and then he condemns it."