The Turnbull government is adamant it won't be splitting its personal income tax package to ease its passage when debate gets underway in the Senate this week.
Finance Minister and chief negotiator in the upper house Mathias Cormann says the government is committed to the whole plan, announced in the May budget as a seven-year, multi-phased tax package.
"We will not be supporting any amendments to split the bill," Senator Cormann told reporters in Canberra on Sunday.
But Labor is equally standing firm, saying it will only back the reductions that start on July 1.
"The only person standing in the way of tax cuts that are to start next month is Malcolm Turnbull," leader of the opposition in the Senate Penny Wong told ABC television ahead of two weeks of parliamentary sittings.
A new low and middle-income tax offset worth up to $530 for individuals will start from July 1, as will an increase in the upper threshold for the 32.5 per cent marginal tax rate from $87,000 to $90,000.
"We have already indicated bipartisan support for that," Senator Wong said.
Under the government's package, further changes are planned for July 2022 which includes more increases to tax thresholds.
But the most contentious is stage three of the plan in 2024 which would increase the top 45 per cent tax rate threshold from $180,000 to $200,000 while abolishing the 37 per cent tax rate, leaving all taxpayers earning between $41,000 and $200,000 on a rate of 32.5 per cent.
"... we are not going to be rushed into signing a blank cheque which has been written by a bloke who won't be around to keep his promise," Opposition Leader Bill Shorten told reporters in Tasmania.
The remainder of the government's business tax plan will again be put to the test the following week.
The government fell short of the crossbench numbers required in the Senate just before Easter and it was not put to a vote.
Labor and the Greens do not back the cut in the corporate tax rate to 25 per cent from 30 per cent for all businesses, meaning the government needs eight of the 10 crossbench senators to pass the legislation.
"I can't imagine that any senator that very carefully considers the national interest, very carefully considers the interests of working families around Australia, could possibly vote against business tax cuts for all Australian businesses," Senator Cormann said.
"Working families around Australia would be the ones paying the price for Bill Shorten's reckless decision to stand in the way of business tax cuts here in Australia."
He declined to say how his negotiations were going with the crossbench.
So far only a tax cut for companies with a turnover of up to $50 million has passed the parliament.
