The report by Human Rights Watch shows that Saudi Arabia has hit factories in Yemen using UK-made weaponry, including a Paveway guided bomb and a Hakim cruise missile, according to the Campaign Against Arms Trade (CAAT), Middle East Eye reported.
Andrew Smith, CAAT's spokesperson, said the report was the strongest confirmation yet that UK weapons are being used on civilians, and would form part of its court challenge against the British government to end weapons sales to Saudi Arabia.
CAAT last month won the right to a judicial review of arms exports to Saudi Arabia, arguing that the British government could not guarantee UK-made weapons were not being used by Saudi Arabia against Yemeni civilians.
"The report presents clear and compelling evidence of UK bombs being used against businesses and civilian targets," Smith said.
"Saudi Arabia has been widely accused of breaking humanitarian law, and yet the arms sales have continued. It is imperative that the government acts on these allegations and ends arms sales to Saudi Arabia.
"The evidence provided by HRW will compliment evidence we already have for the judicial review," said Smith. "The evidence contained in this report is very thorough and we hope will be taken very seriously by the government.
“We didn’t launch the judicial review just to spark discussion, but also to create change. It has to be stressed that KSA is not just a buyer of UK arms. It is by far the largest buyer of UK arms, and this judicial review will go to the heart of UK arms export policy."
The Human Rights Watch report collected evidence from Yemen of what it said was the indiscriminate targeting of 13 civilian economic structures in 17 raids by the Saudi-led coalition, including food warehouses and a soft drinks factory.
HRW said 130 civilians were killed and 171 injured in the attacks, which contravened international law.
The report says the group found remnants of US-made munitions at four sites and remnants of UK-made munitions at three.
One of those munitions, a Paveway IV guided bomb, was produced in May 2015, meaning it was transferred to Saudi Arabia after the start of its aerial campaign in Yemen.
Another site was hit by a UK-made Hakim cruise missile, which was produced by a British company in the 1990s.
Middle East Eye reported earlier this year that British forces continue to train their Saudi counterparts to use an updated cruise missile, the "Storm Shadow", which campaigners say has also been used in Yemen.
Saudi Arabia has led a coalition of nine Arab countries in a military campaign against Yemeni popular resistance forces since March 2015.
According to CAAT, the UK government has since approved £2.8bn ($3.6bn) of weapons sales to Saudi Arabia, despite claims of grave human rights violations committed by coalition forces, FNA reported.
212