Liam Fox - both sides have CWs

Liam Fox on The Daily Politics said that both sides in the Syrian conflict possess chemical weapons (Brillo looked a little startled, but didn't follow up).

Earlier this year Carla Del Ponti - a member of the UN Commisssion of Inquiry on Syria -claimed Syrian rebels had used chemical weapons, but this was off-script and she has been side-lined since then.

Was this a slip by Fox?