Federal Labor has decided to oppose most of the Government's income tax plan, arguing it is unfair and irresponsible.
But the Government still hopes to win enough crossbench support to have the whole plan passed by the end of next week.
The first round of the Government's seven-year tax plan is up to $200 for low-income earners and $530 more for middle-income earners to be delivered in tax returns after July next year.
Opposition Leader Bill Shorten said Labor would vote for that section immediately because it would help with the cost of living and low wage growth.
He demanded the bill be divided into separate parts so that could happen.
But the Government has insisted it is not prepared to split the tax plan.
Instead it will try to win enough Senate support without Labor and the Greens.
Mr Shorten has promised that if the Government succeeds in passing the tax plan with crossbench support, a Labor government would repeal the tax cuts.
That sets up an election fought on the amount of personal tax people pay.
Government accused of tricky politics
Mr Shorten criticised the Government for promising tax cuts so far into the future, calling it a "tax trick".
"We say to the Government, if you want to talk about promises in more than two election cycles' time, take these radical proposals to the people of Australia and see what they think about them," he said.
Key parts of Treasurer Scott Morrison's tax plan do not kick in until July 2022.
The final section would happen in July 2024, when everyone earning between $41,000 and $200,000 would pay the same rate of tax.
Independent senator Tim Storer also said he would not agree to the full seven-year tax plan, calling it bad policy and tricky politics.
"It would handcuff future parliaments two elections into the future to massive — and quite possibly unaffordable — reductions in revenue," Senator Storer said.
"It holds out a bribe to voters of a pot of gold at the end of the rainbow, but not for another seven years."
But despite Labor, the Greens and Senator Storer opposing the full plan, the Government is optimistic it can still get enough support to pass the entire package.
It needs the backing of eight crossbenchers and already has five senators on board.
The two Centre Alliance senators (formerly Nick Xenophon Team) are still deciding whether to support the third stage of the plan, but have not ruled out backing it.
Pauline Hanson and her One Nation colleague Peter Georgiou have also not committed to backing the full plan.
