As Cameron arrived for G20 Summit in Russia, he told reporters that scientists at the Porton Down laboratories have been 'examining samples' from Syrian capital, Damascus.
The Ministry of Defence confirmed reports that they found traces of sarin gas on cloth and soil samples.
According to the BBC, Cameron also denied claims he had 'no hand to play' over Syria after his Commons defeat on UK military action.
He said the UK would lead calls for more action on aid for refugees and push for fresh peace talks.
Syrian President Bashar al-Assad is accused of using chemical weapons against civilians on several occasions during the 30-month conflict, most recently on a large scale in an attack on 21 August on the outskirts of the capital.
Assad regime has denied involvement and said the rebels were responsible.
But Cameron said evidence of the Assad regime's use of chemical weapons was 'growing all the time,' the report added.
--ANI (Posted on 06-09-2013)