Foreign Minister Penny Wong clashed with Liberal deputy leader Jane Hume, saying she could not 'handle the truth' after she was questioned about the Federal Budget.

The Albanese government secured a deal with the Greens on Tuesday to pass changes to capital gains tax (CGT), including replacing the 50 per cent discount with a 30 per cent flat tax indexed to inflation.

Certain 'innovative' companies will be exempt from the changes. 

Negative gearing rules will be tightened, limiting the popular tax concessions to newly built properties and grandfathering all existing arrangements before May 12. 

The Coalition has accused the government of misleading voters after Prime Minister Anthony Albanese told voters in the run-up to the 2025 election that they were not under consideration.

During Senate Question Time on Tuesday, Liberal frontbencher James Paterson asked how the government defines a 'small business' and an 'innovative business' for exemptions.

But Wong was unable to explain who would differentiate between firms and accused Senator Paterson of staging a political stunt.

'Well, now we see the whole point of the question, which was re‑asking yesterday's question, is so Senator Paterson could deliver that grab in the last minute,' she said.

'And I look forward to his social media clip on this, but it will not hide the fact that you are a policy‑free zone.'

The exchange escalated when Hume interjected repeatedly from the Opposition benches and Wong turned her attention to the Liberals' deputy leader.

'You went to the last election with higher taxes, Senator Hume,' Wong said.

'Senator higher taxing Hume... Senator higher taxes Hume... is now the deputy leader of the Liberal Party.'

Shouting, Hume said: 'You lie, you lie, you lie.'

But Wong, quoting Jack Nicholson's line from the 1992 film A Few Good Men, said: 'You can't handle the truth!'

The quote comes from a scene in the 1992 film A Few Good Men, in which Navy lawyer Lieutenant Daniel Kaffee, played by Tom Cruise, questions Nicholson's character about an illegal disciplinary order - a 'Code Red' - that led to a marine's death.

Following the heated exchange, Hume told the Daily Mail that Wong's response showed that Labor 'lied'.

'I wasn't asking who ordered the Code Red but she chose to go full Jack Nicholson, so I'll take that as a confession,' she said. 

'In the heat of the moment Penny Wong finally admitted what Australians already know - Labor lied.' 

The clash comes as the government is set to have its tax changes passed through the Senate as soon as Thursday.

Under the deal with the Greens, the Labor government will close a loophole where people can buy property through self-managed super funds and access a capital gains tax rate of just 10 per cent.

'These changes don't in any way change the tax arrangements for superannuation, [they] don't impact any existing SMSF borrowing arrangements and provide time to finalise arrangements that are in train,' the Albanese government said in a statement.

The Greens have also forced the government to extend the inquiry into its proposed changes to the National Disability Insurance Scheme (NDIS) by eight weeks.

In the Budget, Labor proposed cutting as much as $36billion from the NDIS over four years, a move critics warn could see up to 160,000 people removed from the scheme.

The Greens have fiercely opposed the cuts.

While Labor has supported a number of amendments to the NDIS legislation, the minor party says it will still vote against the bill in its current form.

It remains unclear whether the government will proceed with aspects of its agreement with the Greens if they ultimately oppose the NDIS legislation.

Albanese said the Greens had failed to back necessary changes, telling the Daily Mail they 'have not supported reform that's necessary for NDIS' when asked whether the deal would remain if the bill is voted down. 

The tax changes will be debated this week before a vote on Thursday.