SNP Westminster leader Angus Robertson demanded at Prime Minister’s Questions to know whether missiles partially built in Scotland had been used in possible war crimes.
The government has faced criticism for selling arms to Saudi Arabia, which is involved in a civil war in Yemen pitting the western-backed government against Shiite rebels. The conflict has killed thousands of civilians since it erupted in 2015.
Mr Robertson said that if the Prime Minister could not confirm whether UK-built weapons had been responsible for civilian deaths, “how can you possibly in good conscience continue selling them to Saudi Arabia?”
Mrs May replied: “As you know we have one of the toughest regimes in the world in relation to arms exports.
“When these allegations arise then we have been pressing, I have pressed in the past and the Foreign Secretary has pressed the Saudi Arabian government to properly investigate these issues and to learn the lessons from them.” She added that Saudi Arabia was an important ally on counter-terrorism and security.
A Number 10 spokeswoman later said information on Saudi strikes that may have killed civilians was being shared with the UK.