Cameron didn't debate Salmond and the referendum went to the wire.
Is it any wonder that Cameron won't debate Farage?
Their are cries of "chicken" and "running scared" as well as "frit" from too many respected political commentators to mention. There is talk of Cameron taking the hit now rather than being frit against Farage and taking a pounding from the People's Army in a live TV debate just weeks before the general election.
I don't blame Cameron. If I were him, i would be going around shouting "for Gawd's sake, can we please cut the green crap?" and "we're doomed, I tell you, we're doomed".
He has probably been told "Don't panic, Mr Camwairing, don't panic, take the hit now rather than the certain pounding from Farage in the future".