Members of the House of Commons reviewed the alleged use of chemical weapons in a suburb outside of Damascus. U.N. inspectors in Syria surveyed the site earlier this week. Hundreds of civilians were allegedly killed in the attack last week.
John Day, chairman of the British Joint Intelligence Committee, issued a three-page letter Thursday to British Prime Minister David Cameron on his assessment on the chemical weapons claims.
"There is no credible evidence that any opposition group has used chemical weapons," his letter said. "A number [of rebel forces] continue to seek a chemical weapon capability, but none currently has the capability to conduct a chemical weapon attack on this scale."
Supporters of Syrian President Bashar Assad blamed rebels for the incident, saying they were trying to court international favor. Day said there was "some intelligence" to suggest Assad's government was behind the attack.
"Extensive video footage" of the scene, which Day say would be difficult to fake, showed people suffering from exposure to a nerve agent like sarin.
He added the Syrian government likely used chemical weapons on 14 different occasions last year.
Day said the British intelligence linking the Syrian government to the Aug. 21 attacks outside Damascus was "limited but growing."
The British government offered a draft proposal at the U.N. Security Council for military intervention in response to the chemical weapons claims.