Voters have categorically rejected Prime Minister Tony Abbott's increase to the pension age of 70. A fresh poll shows two-thirds of voters oppose the plan.

Before a tough budget expected to include cuts to family payments and a rise in petrol excise, an exclusive Fairfax ReachTel poll has found strong opposition to extending the pension age. The backlash has led to the combined Liberal and Nationals vote dropping to 38 per cent before preferences compared to the ALP, which is on 40 per cent. That is a fall on the Coalition primary vote of 8 percentage points after it secured 46 per cent of first preference votes at the September 2013 election.

The Greens party remains around its election mark of 11 per cent, leading to a two-party-preferred result between Labor and the Coalition, based on preference flows at last year's election, of 54-46 in favour of the ALP - virtually reversing the election result.

But the poll also shows the government has won support for its controversial deficit tax plan. More than half of all voters think a hit on high income earners is justified to rebalance the budget.