A UN panel in January found 119 air strikes by the Saudi-led coalition in the country potentially breached human rights law.
The UK is the second biggest arms dealer in the world and Saudi Arabia is it's biggest customer, implicating British-made Brimstone missiles and Typhoon missiles in the fighting.
“At the moment, we do not think the threshold has been crossed," the Foreign Secretary said on the BBC's Andrew Marr Show.
“So far we do not believe there has been a clear risk of breach of humanitarian law in respect of the use of those weapons.”
He reaffirmed British allegiance to the Kingdom, saying the "UK is supportive of Saudia Arabia", while the country bombs Yemen.
Yet he denied that British experts were involved in picking exact targets of Saudi-coalition air strikes, saying they were simply giving "general guidance" and "trying to advise them on how targeting should work”.
The Saudi-led coalition has been accused of bombing multiple international hospitals run by the charity Médecins Sans Frontières, as well as schools, funerals and wedding parties.
Strikes on a wedding in September killed 131 people, including children, in the capital Sannaa.
One attack on a funeral left at least 140 dead. At first the Saudis denied any role in the lethal attack, but later admitted it had "wrongly targetted" civilian mourners.
The slaughter and starvation of Yemeni civilians, caught between the Saudi bombardment and the country's Houthi rebels, has continued with little respite since the country spiralled into a civil war in 2015.
An estimated 10,000 people have been killed and 83 per cent of the population are now in need of humanitarian assistance.
In response to the foreign secretary's statements, director for arms control at Amnesty International UK said: "The Foreign Secretary is ignoring the real threshold here — the one that divides an approach to selling arms responsibly based on our arms trade controls system, and the UK's present cavalier approach to selling weaponry to Saudi Arabia.
"As Mr Johnson should know, where there's a clear and continuing risk that any UK arms sold to Saudi Arabia could be used to commit breaches of international humanitarian law in Yemen, the UK should immediately suspend all such arms sales.
"Time and time again, the Saudi coalition's attacks have hit hospitals, schools, funeral halls and homes, and thousands of Yemeni civilians have been killed and injured.
"Mr Johnson is ducking his responsibility to prevent the UK being party to the unlawful killing of civilians in Yemen".
Since 2010 Britain has also sold arms to 39 of the 51 countries ranked “not free” on the Freedom House "Freedom in the world" report, and 22 of the 30 countries on the UK Government’s own human rights watch list.
Saudi Arabia has rejected numerous accusations of human rights violations in Yemen, including the use of cluster bombs.
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