The fact that bitter enemies accuse each other does not mean that it is not true, nor that both accusations are accurate.
Take for example recent Sarin attack in Syria. Perpetrated by the British mercs and AQ against Syrian civilians.
UKUSA blame Syrian goverment, although they have the hard facts, like the rest of the world. Syria blames AQ terrorists affiliated with UKUSA but has no 00 to blame UKUSA.
One could say they are blaming each other, which is not true, one side is making false accusation to protect it's actions, another is pointing in the right direction.
Ditto for Halabja when Iran was accused although having nothing to do with it.
This is an allegation, not a fact. Unless you've seen evidence I haven't.
I wouldn't be surprised if AQ were involved, but I hope the Brits wouldn't do this.