Re: General Sir Michael Rose calls for Tony Blair's Impeachment
The real issue here is that Tony Blair did not declare "War" on anyone, he simply committed the UK armed forces to a certain act that was loosely based on UN mandates.
I think you would also have to include the Chiefs of Staff, the Defence Minister, the leader of the loyal opposition, the legal advisors to the PM, and Cabinet as well, if you were to try something like this.
"Impeachment" as such does not exist as such in the UK but you could certainly have a number of MPs put forward a Commons motion of impeachment, not that I think this would get anywhere, wasn't it tried last summer?