Australian voters are worried they'll be worse off after Prime Minister Kevin Rudd's first budget, an opinion poll found today, but the deeply divided conservative opposition was ill-placed to take advantage.

Rudd's centre-left Labor government won power last November and delivered its first national budget on May 13, handing tax cuts to workers and families and penalising the wealthy to pay for a surplus designed to rein in inflationary pressures.

But a Galaxy poll published in News Limited newspapers on Monday found only 23 percent of voters believed they would benefit from the budget, while 33 percent said they would be worse off and 44 percent were uncommitted.

"We didn't frame the budget with our eye on opinion polls," Treasurer Wayne Swan said today, after major newspapers headlined the poll "Swan Dive".

Rudd's government has enjoyed strong support since last year's election, with the polls showing government support running five points above its election showing and with Rudd's personal approval soaring above 70 percent.

The budget, however, has angered pensioners who complained it gives them no help at a time of rising prices. The Galaxy poll found 41 percent of voters over the age of 50 believed they would be worse off.

Conservative Liberal Party leader Brendan Nelson has also attacked government decisions to raise taxes on pre-mixed alcohol drinks and to cut subsidies for people who install solar power.

Nelson used his televised budget reply speech to try to boost his personal approval rating, languishing below 10 percent, by promising to block higher taxes on pre-mixed drinks, and to cut petrol excise by 5 cents a litre if his party returns to power.

But Nelson's attacks on the budget were undermined when an e-mail from his treasury spokesman and leadership rival Malcolm Turnbull revealed Turnbull had told Nelson his promise to lower petrol prices was bad policy. The e-mail, leaked to Australian newspapers, reignited tensions between Nelson and Turnbull, who contested the leadership in the wake of John Howard's resignation after the November election defeat.

Political analysts said Nelson was unlikely to face an overt challenge until early 2009, well ahead of the next election due in late 2010, although his promise to cut petrol prices had created new political problems for his party.

"In the long term it threatens the Liberals' economic credibility and creates a huge headache for whoever leads the party to the election," Sydney Morning Herald political correspondent Phillip Coorey wrote today.

The Australian Financial Review's Geoffrey Barker said Nelson's attacks on Labor's budget made it harder for the party to recover from last year's election loss. "Moving to block the first budget of a new and popular government can only be counterproductive and compound Liberal difficulties," he wrote.