Opposition Treasury spokesman Joe Hockey has suggested the Coalition was double-crossed by Tasmanian independent Andrew Wilkie over a controversial $1 billion offer to rebuild the Royal Hobart Hospital.

Throwing in his lot with Labor yesterday, Mr Wilkie said he had rejected Opposition Leader Tony Abbott's offer of the cash because he thought it was "reckless" and because Mr Abbott had not explained where the money would come from.

Instead, Mr Wilkie agreed to support Labor in return for $340m for the hospital and commitments on gambling reforms.

But the Coalition disputes Mr Wilkie's version of the negotiations, saying he was the one who asked for the billion-dollar spending commitment.

When asked on Radio National whether Mr Wilkie had "double-crossed" the Coalition, Mr Hockey replied: "Good question."

Mr Hockey said Mr Wilkie never asked where the funds would come from.

Opposition finance spokesman Andrew Robb joined the attack, saying Mr Wilkie lobbied hard for substantial funds for the hospital.

"I find it somewhat odd, his claim yesterday," he told AM.

"It is a bit ironic that he spent a week-and-a-half trying to desperately convince Tony Abbott that this was not only, not reckless, but the most responsible thing that he thought could be done."

"He went to great lengths to explain why this money would be better spent on a major hospital for Tasmania."

Last night Mr Robb told Lateline the Coalition was still committed to spending the cash on the hospital, even without Mr Wilkie's support in parliament.

He denies that Labor's deal with Mr Wilkie puts the Coalition at a disadvantage, saying he finds it "inconceivable" that the three country independents would side with Labor and the Greens.

"It would destroy Australia, the country Australia, to have a Labor Green coalition running this country," he said.

"It would be the most left wing government in Australian's history if they take the reins next week."

Mr Wilkie maintains the offer was irresponsible.

"He [Mr Abbott] simply offered me $1 billion, no strings attached, no discussion of where the money was coming from," he told Radio National.

"We need to make sure this isn't just an exercise in pork-barrelling."

Mr Wilkie's decision to back Labor means it is now just two seats short of a majority, compared to the Coalition, which needs three extra seats.

The remaining trio of unaligned independent MPs are likely to use the weekend to finalise their decision before making a deal next week.

Independent MP Tony Windsor says he will be spending most of today considering his position.

"Today is about actually sitting down and putting some stuff on paper," he said.