One Nation MP Barnaby Joyce has panned Treasurer Jim Chalmers’ denial that he backtracked on his budget, after Labor unveiled its capital gains tax carve-outs for businesses.

The government on Thursday lifted the “small business” threshold from those with turnover of $2 million to turnover of $10 million, flagged a start-up concession and exempted testamentary trusts from planned CGT changes.

Mr Chalmers told Sky News Australia the changes did not constitute a “backflip”, instead labelling them the outcome of consultation announced at the budget.

Mr Joyce asked if the carve-outs were not a “big enough back down” for anybody else.

“Jim, what does a bus look like when you’re underneath it and it’s driving over you,” he told the Bolt Report.

“Talk about the Prime Minister throwing his Treasurer under a bus, which he had to do because you should have seen the budget.”

One Nation’s freshly-promoted treasury spokesman said he could see Labor preparing to “back down” since the budget was unveiled at the beginning of May.

“It’s a disaster, I mean, we can see this coming a mile away… you can hear the churning of this bus warming up in the back room,” he said.

“Its driver is the Member for Grayndler (Prime Minister Anthony Albanese) and Jim is called, I don’t know, tarmac, because he’s just gone straight over the top. It was a disaster.

“It was the most panned budget in my time in politics, a complete train wreck.”

Mr Chalmers and Mr Albanese softened the impact of their capital gains tax overhaul for businesses following significant outcry over the budget plans.

“We will increase the new threshold by five times, bringing it into line with the threshold for small businesses in a number of other features of the system,” Mr Albanese said.

“We’re also proposing to introduce a new innovative business tax concession for start-ups and will release the consultation paper on the start-up sector.”

The turnover threshold for small businesses to access the 50 per cent capital gains tax discount was lifted from $2 million to $10 million.

The carve-outs will also provide a 50 per cent capital gains discount to early stage investors and founders, as well as employee share scheme participants.

“We will put out a fair bit of detail on our position and we will be seeking feedback on that in the coming weeks,” Mr Chalmers said.

Mr Albanese also revealed discretionary trusts would be exempt from the minimum 30 per cent tax where they were used for “genuine testamentary purposes”.

Mr Chalmers confirmed the legislation, currently in the Upper House, would be updated to include these changes.

It comes after the Albanese government clashed with the start-up sector, which warned the previously announced reforms would damage innovation.

Labor’s original plan scrapped the 50 per cent CGT discount and replaced it with inflation-adjusted cost base indexation combined with a 30 per cent minimum tax rate on capital gains.

In his budget speech, Mr Chalmers said the measures were intended to “level the playing field for workers and first home buyers”.

However, while the reforms were framed around housing affordability and intergenerational equity, the impact on the start-up sector quickly emerged as a major concern and eventually forced the government to change course.