The leader of Yemen's rebel Houthi government on Wednesday accused Britain of war crimes by supplying weapons that Saudi-led forces were using to "bomb the people".
Abdel Aziz bin Habtoor said Britain had "sold cluster bombs to Saudi Arabia" that it knew would be dropped on Shiite Huthi rebels fighting the internationally-recognised, Saudi-backed administration of President Abedrabbo Mansour Hadi.
"I don't think they are guilty of war crimes, I believe so," he told broadcaster Sky News. "They are participating in the bombing of Yemen people."
In response to a parliamentary question about the allegations, Prime Minister Theresa May told MPs that Britain had a "very strict regime for export licences in relation to weapons".
"We exercise that very carefully, and in recent years we have indeed refused export licences in relation to arms, including to Yemen and Saudi Arabia," she added.
"Where there are allegations of breaches of international humanitarian law, then we require those to be properly investigated."
The United States on Tuesday blocked the transfer of precision munitions to ally Saudi Arabia, amid anger about the civilian death toll from the kingdom's bombing campaign in Yemen.
"This reflects our continued, strong concerns with the flaws in the coalition's targeting practices and overall prosecution of the air campaign in Yemen," said the White House.
Saudi Arabia has been a long-term ally of the US and Britain in the Middle East, but British Foreign Minister Boris Johnson last week was rebuked by his government after accusing the country of backing "proxy wars" in the region.
In March 2015, the Saudi-led coalition launched air strikes against Iran-supported Shiite Huthi rebels and their allies after the rebels overran much of Yemen.
Since then, the rebels have been pushed out of much of Yemen's south, but they still control nearly all of the country's Red Sea coast as well as swathes of territory around the capital Sanaa.
More than 7,000 people have been killed in the conflict, according to the United Nations. Millions of others are dependent on food aid, with nearly 2.2 million children acutely malnourished due to the near-collapse of the health system during the conflict.