Hundreds of tonnes of chemicals "likely" to have been used by Syria to make the deadly nerve gas sarin were exported by British firms in the 1980s, Foreign Secretary William Hague said Wednesday.
Hague said the chemicals, which can be used legitimately for making plastics and pharmaceuticals, were exported by unnamed British companies to Syria between 1983 and 1986.
"We judge it likely that these chemical exports by UK companies were subsequently used by Syria in their programmes to produce nerve agents, including sarin," he added.
Sarin has been linked by Western powers to a string of attacks during the Syrian conflict, which has left over 160,000 people dead in more than three years.
Signup to our newsletter and follow us on Facebook and Twitter!
The United Nations says there was "clear and convincing evidence" that sarin was carried into the opposition-held Damascus suburb of Ghouta on surface-to-surface rockets in August last year.
The US had threatened to take military action against Syria following the attack, which killed around 1,400 people, but ultimately shied away from strikes.
An international operation to destroy Syrian chemical weapons, negotiated after the Ghouta attack, is now in its final phase.
Controls on exports of such chemicals from Britain were introduced after the sales took place, in the mid-80s, Hague said, insisting that "such exports could not happen today."
His remarks came in a written statement to parliament issued after the BBC first reported the claims this week.