Taxpayers foot multimillion-dollar advertising bill in final days before election is called

Tender documents show taxpayers are on the hook for $252 million in government advertising that has been already spent or can be spent before the campaign begins.

The spending comes as Labor calls on the government to commit now to higher tax cuts for workers earning less than $48,000 a year so the Australian Tax Office can implement the benefit when people lodge their tax returns after July 1.

With an election expected on May 18, the Parliament may not have time to legislate the tax cuts before June 30 even if both major parties agree on the immediate changes, including a tax offset worth up to $1080 for 10 million workers.

The advertising on television, radio and billboards includes the "building our future" campaign to tell voters about road projects, a "better tax" campaign about personal tax cuts, a "quality schools" promotion about school funding and a "powering forward" campaign about cutting energy bills.

Labor estimates the outlay on advertising has averaged about $600,000 a day but there are no daily figures on the spending, which means it could intensify before the election is called.

Prime Minister Scott Morrison held off from calling the election on the weekend and appears likely to name the date within a week, fuelling expectations Australians will go to the polls on May 18.

Mr Morrison mentioned May 25 as a potential election date in a radio interview on Friday but the Australian Electoral Commission and the Parliamentary Library have previously named May 18 as the last possible date.

Treasurer Josh Frydenberg justified the advertising spending by saying Labor did the same when it was last in power.

Labor estimates the AusTender advertising contracts were worth $252,276,527.80 over the period from January last year to the end of February this year, a daily spending rate of $600,659.

But Labor engaged in the same campaigns when it was in government in 2013 and it spent $6.5 million in Australian publications on a border protection campaign meant to deter people smugglers in Indonesia.

A senior public servant later said he had to authorise the campaign during the caretaker period due to a "legal direction" from the Labor government.

The spending rate would amount to $4.8 million over eight days before the writs are issued before the election, depending on when the election is called and the average daily spending rate.

Labor and the Coalition agree on the tax offset worth up to $1080 for workers earning between $48,000 and $126,000 a year, although Labor is opposed to the later stages of the government plan.

Labor promises a higher offset for the 3.6 million workers earning less than $48,000 a year.

Under the Labor policy, workers earning up to $37,000 a year will receive a tax cut of up to $350. For workers earning between $37,000 and $48,000 a year, the value of the offset will increase up to the maximum offset of $1,080.

This costs $1.05 billion compared to the government plan.

While the Australian Tax Office might be able to implement the changes if it was confident they would become law with support from both major parties, the House of Representatives is unlikely to meet again until after the election.

Neither side has committed to scheduling Parliament before June 30 to pass the tax changes.

Labor treasury spokesman Chris Bowen said the government had delayed calling the election in another sign of the "chaos and dysfunction" of this term of Parliament.

"A later election date makes more difficult the passage of income tax cuts from 1 July," he said.

"If the government supports Labor's bigger, better and fairer income tax cuts, particularly for those earning below $40,000, then they should make that clear so the ATO can prepare for those to start from 1 July."

Mr Frydenberg played down the concerns over the ability to implement the changes.

"Should the government be re-elected, the timing of the election will not affect low and middle income earners receiving a benefit of up to $1080 - or up to $2160 for a dual income family," he said.

"Taxpayers will be able to access the offset after they lodge their end of year tax returns from 1 July 2019, which is in just 13 weeks' time."