Mr Robb would not confirm or deny speculation he may take over as leader should Mr Turnbull stand down from his position, saying only that Mr Turnbull had the party's full support.

Doubt was cast over Mr Turnbull's position as leader after his disastrous handling of the OzCar scandal, with suggestions Mr Robb was considered a contender.

"Enough has been said about that. We are all behind Malcolm. Malcolm will lead us to the next election and we will be very competitive," Mr Robb told reporters in Sydney.

"The way in which he took the government to task over debts and spending after the budget shows he has got exceptional ability to deliver a message and keep the government accountable.

"I have got every confidence he will do that in the run down to the next election."

Mr Robb said every contest was winnable, but admitted it would be difficult for the coalition to win the next election.