Well, Hockey wouldn't be a pollie if he didn't exploit that golden opportunity to put in the boot. And he's right to cast doubt on the likelihood of a $6.6 billion surplus in four years' time - not because the government has got at Treasury and Finance but because no one, not even Hockey, can have any certainty about how the economy will unfold between now and then.

That's just common sense. It's the simple souls who take medium-term projections literally that Hockey should be wising up, not implying he can know the future better than Swan can, or that Treasury's forecasts would be right on the money were Swan not forcing them to be wrong.

There's no reason to believe a change of government would make any difference to the likelihood of budget forecasts proving off-beam because of unforeseen developments. The world will not suddenly become more stable or predictable on September 14.

But I think Hockey's motives in rubbishing the budget forecasts are more devious. He dribbles out the odd example of unpopular spending cuts but, since he doesn't know the budget's true position, he can't do more than that. He doesn't know how much he's got in the kitty to play with - or, rather, how big is the ''true'' deficit that will constrain the promises the Coalition will make. Get it? He claims the budget figures are politically tainted because this justifies him delaying publication of his costings until only about three weeks before election day - which is when we'll receive the PEFO, the pre-election economic and fiscal outlook, signed off not by Swan and Penny Wong, but by the secretaries of Treasury and Finance.

The ''pee-foe'', part of Peter Costello's charter of budget honesty, is a good idea gone wrong. It's purpose was to stop future incoming governments doing what Costello did in 1996 (and Paul Keating did in 1983): claiming to have uncovered a ''budget black hole'' left by their predecessors and using this as a excuse for a horror budget, in which cuts not mentioned in the campaign materialise and promises retrospectively declared to be ''non-core'' are broken.