This is not the week ending Prime Minister Kevin Rudd needed as he geared up for the final seven-day stretch of the campaign for next Saturday's Australian election.
He hoped to win points from anxious Australian voters with suggestions that foreign investment rules could be tightened. It turned out to be a thought bubble that none of his senior colleagues had any idea was coming.
Rudd claimed that independent bureaucrats had uncovered a A$10 billion ($11.5 billion) hole in Opposition costings. Instead, the depart-ments said they had found no such thing.
And as he tried to bluster his way through, a new poll said the voters of western Sydney were swinging so hard towards Opposition leader Tony Abbott that they alone could bring down the Government.
The weekend will bring another welter of polls to test whether Rudd has any hope at all of turning the campaign around before Australians head for the ballot box.
On trends so far, that seems a far distant prospect.
A frantic final week begins on Monday with Abbott's campaign closing speech at the National Press Club in Canberra, followed later by the release of the full policy costings he has so far refused to reveal.
Rudd will continue hammering at Abbott's credibility and alleged preparations to cut spending to the bone. Rudd's campaign wrap-up will be delivered at the Press Club on Thursday.
But Rudd has damaged himself with his bungle over Abbott's costings. It undermines Labor's strategy of painting itself as honest broker and Abbott as the economic devil incarnate. Worse, it makes Rudd look like a fool.
Abbott's consistent refusal to publish the figures underlying his policies and the savings that would pay for them had given Labor a free run to claim the Opposition was concealing a hidden agenda.
Rudd has been running hard on unsubstantiated and disputed claims the Opposition was hiding a A$70 billion hole in its policies: an apparent multi-billion-dollar gap in claimed Opposition savings of A$31 billion was the icing.
Rudd said the gap had been uncovered in assessments of the costings by the Treasury, Department of Finance and the Parliamentary Budget Office, which found the savings in fact totalled only A$21 billion.
Claiming the Opposition had made substantial errors in its calculations, Rudd said: "It is quite clear that there is now a massive A$10 billion hole in the A$30 billion that they are claiming."
Rudd crashed to earth within hours. Treasury Secretary Martin Parkinson and Finance Secretary David Tune issued a statement saying they had examined policy and options presented by the Government, not the Opposition's policies, and that any costings made before the election could not be applied to policies announced during the campaign.
"At no stage prior to the caretaker period has either department costed Opposition policies," the statement said. "Different costing assumptions, such as the start date of a policy, take up assumptions, indexation and the coverage that applies, will inevitably generate different financial outcomes."
Faced with the statement and its inevitable backlash, the Government is sticking to its guns. Finance Minister Penny Wong said the costings it used had been based on statements made by the Opposition, and if Abbott claimed they were wrong he should disclose his figures in full.
Abbott stands by his costings and scoffed at Labor: "Mr Rudd has got all of his own figures wrong and now he's getting our figures wrong too. When it comes to budget figures, if Mr Rudd's lips are moving, you know he's not telling the truth."
The row will not help Labor in western Sydney, where a Newspoll in the Australian newspaper yesterday said support had collapsed to the catastrophic levels of former Prime Minister Julia Gillard.
It said that with a swing three times the shift to the Coalition in national polling, at least eight Labor seats were in real danger of falling. Casualties could include Treasurer Chris Bowen and his assistant, David Bradbury.
The Opposition is also likely to claim disgraced former Labor MP Craig Thomson's seat of Dobell, along with the Robertson seat, north of Sydney, and the two New South Wales seats of retiring independents Tony Windsor and Rod Oakeshott.