The first chance to put the tax bills to a vote in the Senate comes in the week beginning on June 18, with just eight sitting days to decide the bills before Parliament rises on June 28 for its winter recess.

In a boost for the government ability to negotiate with the Senate, former Liberal independent Steve Martin announced on Monday he would join the Nationals, which means the Coalition needs eight out of 10 crossbenchers to pass a bill. It was previously nine out of 11 crossbenchers.

The first government bill sets out personal tax cuts that cost $140 billion over a decade, while the second extends company tax cuts to all businesses at a cost of $35.6 billion over a decade.

One Nation has abandoned its previous support for the overall company tax bill but left the door open to a new deal with a threshold of up to $500 million.

“People can ring my office and they can actually put their message across to me whether they want corporate tax cuts, but let’s look at should we actually bring it in sooner than the eight years down the track,” Senator Hanson told the Seven Network.

Senator Cormann held out hope for a renegotiation with the crossbenchers but said funding for a new coal-fired power station was “not on the table” in any talks with Senator Hanson and dismissed the idea of accepting a $500 million threshold.

“It would be a barrier to growth. If you put an artificial ceiling on the growth a business can claim for, like a disincentive to further growth beyond that threshold, you’re putting a break on jobs growth,” he said.

“It was always designed as a ten year plan. I can’t see that legislating at that level, and locking it in at that level, would ever then be able to be addressed successfully down the track.

“This now needs to be addressed as one package.”

Senator Cormann took a similar approach to the personal tax cuts, saying: “We won’t split the package.”

The government argues that Opposition Leader Bill Shorten must make a decision by June 28 on whether he will stand in the way of personal tax cuts for low-income workers.

When the personal tax cut bill went through the lower house last week, Labor chose to vote in favour of the bill rather than being accused of blocking tax relief.

“Bill Shorten wants to punish people who work hard and make the effort to get ahead. We believe that providing reward, encouragement and incentive to hard-working Australians, encouraging them to get ahead, is good for the economy overall,” Senator Cormann said.

“He’s got to make a decision on whether his anti-aspiration, politics-of-envy vendetta is more important to him than providing cost-of-living relief to middle income workers.”

“We never give up, we stand for the economic national interest,” Senator Cormann said.

Loading

Mr Shorten campaigned on Monday in one of the five byelection seats, the marginal Tasmanian electorate of Braddon, with a message to voters to reject the Coalition in order to stop the tax cuts for big companies.

“We are going to make this byelection an opportunity to send an important message to Mr Turnbull,” Mr Shorten said.

“If you want to give tax cuts to big banks and big multinationals and mega businesses, vote for the Liberals.”

The Senate last year approved a cut in the company tax rate to 27.5 per cent for smaller employers, applying at first for companies with annual turnover of up to $10 million before being extended to companies with turnover of up to $25 million. It will be extended to those with turnover of up to $50m from July 1.

The bill before Parliament seeks to increase the threshold to $100 million from July 2019, to $250 million from July 2020, to $500 million from July 21, to $1 billion from July 2022. The cap is removed and the tax cut flows to all companies from July 2023, with the rate falling to 25 per cent from July 2026.

The changes already legislated cost $29.8 billion over a decade, while those before the Senate cost another $35.6 billion over a decade.

Labor is yet to declare its position on the tax cuts already legislated and would have to revise its policy costings if it chose to accept the cuts, given its only other option is to tell small businesses they will have to give up company tax cuts they have already received.

Treasury figures suggest the 10-year plan would add 1.1 per cent to the economy after the full policy takes effect over a decade.

Because the increase in the economy is permanent, it could expand a $2 trillion Australian economy by $22 billion every year after the first decade. The Treasury modelling is contested by the Grattan Institute, the Australia Institute and others.