A team of international lawyers and a Yemeni human rights group have submitted new evidence of alleged Saudi war crimes to the UK government in a bid to stop the sale of British weapons to the kingdom.

The nearly 300-page report alleges a litany of international law violations by the Saudi-led coalition in Yemen. It further claims that the Riyadh covered up evidence of war crimes in subsequent investigations into deadly airstrikes.

The evidence was collected by researchers from the independent Yemeni rights group Mwatana and submitted to the international trade secretary, Liz Truss, by the Global Legal Action Network (GLAN) and UK law firm Bindmans. It involved extensive on-the-ground research and analysis of airstrikes in which civilians were killed.

“The coalition has continued to carry out apparently unlawful attacks throughout the course of the conflict, failed to credibly investigate, and whitewashed significant civilian harm,” the two organisations said in a statement.

The report specifically takes aim at the coalition’s own mechanism for investigating claims of civilian casualties – the Joint Incidents Assessment Team (JIAT).

The British government has repeatedly used the existence of the team to justify continued weapons sales.

Former prime minister Theresa May said of the process in 2018: “Where there are allegations that activity has taken place that is not in line with international humanitarian law, they [the Saudis] investigate that and they learn the lessons from it.”

Brutal effects of Yemeni war Show all 12 1 /12 Brutal effects of Yemeni war Brutal effects of Yemeni war Yemen organised by the UAE's National Media Council shows a Yemeni woman holding a child diagnosed with malnutrition at a hospital in the southeastern port city of Mukalla, the capital Hadramawt province AFP/Getty Images Brutal effects of Yemeni war Mohamed, 2, is treated for Malnutrition in Mukalla, the capital Hadramawt province, Yemen Bel Trew Brutal effects of Yemeni war a trip in Yemen organised by the UAE's National Media Council (NMC) shows a Yemeni woman holding a child diagnosed with malnutrition at a hospital in the southeastern port city of Mukalla, the capital Hadramawt province. AFP/Getty Images Brutal effects of Yemeni war UAE's National Media Council (NMC) shows a Yemeni woman sitting next to a child diagnosed with malnutrition at a hospital in the southeastern port city of Mukalla, the capital Hadramawt province. AFP/Getty Brutal effects of Yemeni war A picture taken on August 7, 2018 during a trip in Yemen organised by the UAE's National Media Council shows Yemeni women attending to children diagnosed with malnutrition at a hospital in the southeastern port city of Mukalla, the capital Hadramawt province. (Photo by KARIM SAHIB / AFP) (Photo credit should read KARIM SAHIB/AFP/Getty Images) AFP/Getty Images Brutal effects of Yemeni war Mohamed, 2, is treated for Malnutrition in Mukalla, the capital Hadramawt province, Yemen Bel Trew Brutal effects of Yemeni war A Yemeni child suffering from malnutrition is weighed at a hospital in the northern district of Abs, in Yemen's Hajjah province AFP/Getty Images Brutal effects of Yemeni war A Yemeni child suffering from malnutrition awaits treatment at a hospital in the northern district of Abs, in Yemen's Hajjah province AFP/Getty Images Brutal effects of Yemeni war A Yemeni child suffering from malnutrition awaits treatment at a hospital in the northern district of Abs, in Yemen's Hajjah province AFP/Getty Images Brutal effects of Yemeni war Yemeni nurses weigh a malnourished child at a hospital in the northern district of Yemen's Hajjah province AFP/Getty Images Brutal effects of Yemeni war A Yemeni woman carries a malnourished child as she waits during food distribution in the province of Hodeida AFP/Getty Brutal effects of Yemeni war A Yemeni child suffering from malnutrition is measured at a hospital in the northern district of Abs, in Yemen's Hajjah province on August 18, 2018. (Photo by ESSA AHMED / AFP) (Photo credit should read ESSA AHMED/AFP/Getty Images) AFP/Getty Images

But researchers detail at least 12 incidents in which civilians were killed and where the JIAT denied the coalition had carried out an airstrike, despite those claims being “directly contradicted by witness and photographic evidence”.

One such incident was an attack by the coalition on a funeral in the rebel-held city of Hodeidah on 21 September 2016, which killed 23 people, including 5 children.

The new report comes as the British government prepares to respond to a Court of Appeal judgement that forced it to freeze sales of UK arms to Saudi Arabia while it reconsidered whether they could be used to violate international humanitarian law.

The court found in June that the government “made no concluded assessments of whether the Saudi-led coalition had committed violations of international humanitarian law in the past, during the Yemen conflict, and made no attempt to do so”.

Judges said that it was “irrational and therefore unlawful” for the international trade secretary to license weapons exports without assessing past allegations and whether there was a “clear risk” of future breaches.

Riyadh intervened in Yemen’s civil war in 2015 to reinstate the internationally recognised government of Abd Rabbu Mansour Hadi, who was ousted by Iran-backed Houthi rebels.

The United Nations has accused the Saudi coalition of “widespread and systematic” strikes on civilian targets.

The coalition, led by Saudi Arabia and the United Arab Emirates, has admitted to causing civilian casualties in the past, but attributes the deaths to “unintentional mistakes”, and says it is committed to upholding international law.

Together with the US, the UK has played a major role in supporting the coalition’s military campaign against the Houthis – who have also been accused of war crimes by the UN.

The organisations behind the report that they hoped the new evidence would lead the British government to halt all arms sales to Saudi Arabia.

“This evidence will assist the UK government in deciding whether to grant further arms sales licenses for Saudi Arabia,” said GLAN director Dr Gearoid O Cuinn.

“They can either continue to rely on discredited Saudi/UAE-led coalition assurances, or listen to those who have painstakingly documented the constant civilian deaths caused by coalition airstrikes. Multiple European states have already suspended arms sales and now the case for the UK doing the same could not be stronger,” he added.

Labour MP Lloyd Russell-Moyle, who sits on the Committees on Arms Controls in the Commons, accused the government of breaking the law in granting arms export licences for Saudi Arabia.

“Boris Johnson and Sajid Javid both illegally signed off arms export licences according to the Court of Appeal because they failed to consider Saudi Arabia’s record deliberately or recklessly attacking civilians in Yemen,” he told The Independent.