The British government will on Tuesday face the start of a landmark case against arms sales to Saudi Arabia, in a judicial review brought by campaigners who accuse the UK of being complicit in Saudi atrocities during the Yemen conflict.

The case comes before the High Court in London as it emerges that the Ministry of Defence faces fierce criticism for failing to determine whether Saudi Arabia is committing war crimes in Yemen.

The UK has licensed more than £3.3bn of arms including fighter jets, missiles and bombs to Saudi forces since the bombing of Yemen began in March 2015 - and the case could have major repercussions for defence exports.

For almost two years now, the UK has been complicit in the destruction of Yemen - Andrew Smith, Campaign Against Arms Trade

The case, which starts on Tuesday and is expected to last three days, comes as Theresa May’s government is seeking to boost arms exports through post-Brexit trade deals with Turkey and the Gulf states.

Last month, May agreed a £100m fighter jet equipment and support deal with Turkey. This followed briefings from Downing Street that the prime minister was pushing for a multi-billion pound trade deal with the Gulf states, including Saudi Arabia and Bahrain.

The three-day judicial review will determine the legality of the government’s arms transfers to Saudi Arabia. It is being brought by Campaign Against Arms Trade (CAAT) and will include submissions from Amnesty International and Human Rights Watch.

Saudi bombing has contributed to a death toll in excess of 10,000 (AFP)

Andrew Smith, a spokesman for CAAT, said: "For almost two years now, the UK has been complicit in the destruction of Yemen. UK fighter jets and bombs have played a central role in the bombardment, and UK political support has helped to underpin and legitimise it.

"We are always being told that the UK stands for free speech and democracy, yet it has sold billions of pounds' worth of arms to one of the most brutal and repressive regimes in the world to use against one of the poorest countries in the region."

UN and European backing for claim

CAAT’s claim will cite a range of international organisations including a UN Panel of Experts and the European Parliament, which have condemned the ongoing Saudi strikes against Yemen as unlawful.

How many civilians need to be killed, maimed, rendered homeless, and have their hopes and dreams shattered? - James Lynch, Amnesty International

The bodies list a string of violations of international humanitarian law, including disproportionate harm to civilians, damage to essential infrastructure and damage to cultural property.

According to the United Nations, at least 10,000 people have been killed in the war in Yemen between Houthi rebels and the Saudi-led coalition.

A poll of 2,000 adults by Optinium for CAAT recently revealed that 62 percent of UK adults oppose arms sales to Saudi Arabia, with only 11 percent supporting.

Campaigners say the UK is compelled to halt arms sales under global arms treaties and international law if weapons are being used to commit war crimes or in breach of international humanitarian law.

James Lynch, the head of arms control and human rights at Amnesty International, said the British government's repeated refusal to halt arms transfers "beggars belief".

He said there was extensive and credible reporting that showed the "Saudi Arabia-led coalition’s ongoing serious violations of international human rights and humanitarian law, including possible war crimes".

"It is a sad state of affairs that NGOs have to go to court in an effort to force the UK government to do the right thing for the people of Yemen.

"How many civilians need to be killed, maimed, rendered homeless, and have their hopes and dreams shattered by Saudi Arabia-led forces that the UK government, among others, continues to recklessly arm?"

The Yemen war has left the country on the brink of starvation, says the UN (AFP)

'Business as usual'

The British government says that all arms exports are subject to "strict licensing criteria" and that all arms exports fully comply with international and national law.

In addition to calling for the suspension of all existing arms export licences to Saudi Arabia, CAAT is also calling for an investigation into why the British government has failed to hold Saudi Arabia to account over the use of cluster bombs and British jets.

CAAT’s call comes after a number of written answers from ministers in Parliament revealed that the Ministry of Defence had failed to make representations to Saudi Arabia to replace British-built cluster munitions with more accurate weapons.

Responses from ministers also show that the UK has not received assurances from Saudi Arabia that British-built aircraft, such as the Typhoon or Tornado, will not be used to drop cluster munitions.

Andrew Smith of CAAT, told MEE: "When the cluster bombs were first brought to public attention, both the UK government and Saudi forces denied their use. The Saudi regime was forced to come clean, but Whitehall is treating it as business as usual."

"Any military that uses cluster bombs is one that has no interest in minimising civilian casualties. It is disgraceful that we have not been told if UK fighter jets were used during their deployment. The government must call for a full investigation."