Can someone to explain something

Can someone to explain something for me? The Government is, rightly, being forced to justify its reasons for taking our armed forces to war in Iraq. It certainly has got the Government on the defensive. I suppose it is right that the leader of Her Majesty’s Opposition is leading the criticism of the PM. But hang on! Isn’t this the same opposition that, in the run up to the war, was notable for agreeing with the incumbents, only more so?! It seems a little two-faced to me.
As it is, I think the PM needs to either admit that he went to war for political reasons or furnish some evidence that we can all see that substantiates his reasoning. If he does neither, then what little faith his supporters still have will surely wither and fade.