Opposition leader Peter Dutton will promise in his Thursday budget reply that a Coalition government would immediately halve the fuel excise on petrol and diesel.

The cut, which would take the excise from 50.8 cents a litre to 25.4 cents, would be for a year, at a cost of A$6 billion.

The opposition says the measure would mean a household with one vehicle filling up once a week would save about $14 weekly, on average. This would amount to about $700 to $750 over the year, based on a 55 litre tank.

A two-car household would save about $28 a week on average – nearly $1500 over the year.

Legislation for the excise cut would be introduced on the first parliamentary sitting day after the election so it could come into effect “as quickly as possible”.

Dutton contrasted the immediate relief with the longer time frame before people received the tax cuts announced in the budget.

Under the tax changes, taxpayers will receive a tax cut of up to $268 from July 1 next year and up to $536 every year from July 1 2027.

The $17.1 billion income tax package was being rushed through the Senate on Wednesday night, as the parliament readies to rise for the election, that could be called as early as Friday for May 3.

The government wanted to pass the legislation immediately to put the Coalition, which opposed the bill and voted against it in parliament, on the spot.

Also, having the tax cuts in law gives greater certainty to them, as Labor promotes them in the coming campaign.

Dutton said of his proposed excise cut: “If elected, we will deliver this cost of living relief immediately – whereas people have to wait 15 months for Labor’s 70 cent a day tax tweak.”

“This cost of living relief will make a real difference to families and small businesses – everyone from tradies, to mums and dads, to older Australians, and to transport delivery workers,” he said.

“The commute to work, taking the kids to school or sport, the family drive, or the trip to the shops will all cost less under the Coalition. Our plan will save many hundreds of dollars for families across Australia.

"Lowering costs to small businesses, means lower costs for goods and services at the checkout.”

The Morrison government introduced a six-month cut to fuel excise in 2022. The Albanese government declined to extend it when it expired.