The former prime minister fears both sides of the conflict will begin to use chemical weapons as an "acceptable form of warfare" if no action is taken, and urged Britain to help America arm the Syrian rebels, in an interview with The Times.
"I feel very strongly that we are in danger of a failure with catastrophic consequences," he told the newspaper.
"This is no longer a civil war between fractions within Syria. We should be taking a more interventionist line.
"You don't have to send in troops, but the international community should think about installing no-fly zones."
The Prime Minister said the UK believes the "scale of use is sanctioned and ordered by the Assad regime" but also indicated that al Qaida-linked elements in the opposition movement had also attempted to acquire chemical weapons for probable use in Syria.
Translated and edited by The Syrian Observer