ITV News has seen evidence that western weapons - including cluster bombs - are being used against Yemeni civilians by the Saudi-led coalition.
The leader of North Yemen's rebel government, Mohammed Ali Al-Houthi, told our correspondent Neil Connery that Britain should cease arms sales to the Saudis and their Gulf allies, claiming they are being used to kill civilians.
"The British people should be against this war and the suffering of the Yemini people," Mr Al-Houthi said.
"It makes Yemenis feel angry against the British people - all the massacres the coalition carry out are through American and British weapons every day."
Yemen has been in the grip of a civil war for two years.
The Houthi rebel group seized control last January, triggering a Saudi-led military intervention.
The UK's arms sales to the Saudi military are coming under scrutiny as the civilian death toll continues to mount.
have been killed in the war - half of them civilians
ITV news found a US-made cluster bomb canister, said to have been recovered from a village in Hajjah Province, in North Yemen.
Cluster bombs scatter hundreds of bomblets over a wide area.
Many do not immediately explode on impact but maim or kill children or farmers working their land long after they were dropped.
A nearby market in Mustaba was the scene of one of the coalition's deadliest air attacks, killing 119 people, 24 of them children.
It was not possible to identify the source of the bomb fragments found there.
Belkis Wille, the Yemen researcher for Human Rights Watch, told ITV News that after one airstrike, her team found fragments from a bomb which had been made in the UK.
In one airstrike in particular we were lucky enough to find fragments with actually the name of the company still attached.
A government spokesperson said:
The Government takes its arms export responsibilities very seriously and operates one of the most robust arms export control regimes in the world.