Labor senator Jenny McAllister grilled officials on Thursday on the budget papers, which she said showed climate spending “falling precipitously” over the next four years.

Deputy Secretary of the Department of Industry, Science, Energy and Resources Jo Evans was unable to explain a decline in “select climate spending” from $2 billion this year to $1.3 billion in 2025/26.

But she did reveal that a $35 billion investment figure used in the taxpayer-funded “positive energy” campaign reflected the total investment in renewable energy that had occurred, not federal action.

Senator McAllister was concerned that ABC’s Four Corners had reported the federal government as saying it had invested over $35 billion in renewables over the past five years.

“We have never characterised it as an expenditure by government,” Ms Evans said.

“It’s certainly been stimulated by government policies, including Commonwealth government policies, but it also reflects expenditure by the private sector and by state and territory governments as well.”

Greens senator Sarah Hanson-Young was equally sceptical about what she described as the “assertion” that $22 billion was being spent on clean energy technologies through to 2030.

Evans explained the figure included $12.9 billion, or $1.3 billion per year, for the Clean Energy Finance Corporation (CEFC) and $1.4 billion in base funding for the Australian Renewable Energy Agency (ARENA).

Evans said the $22 billion figure also included “one or two things not yet publicly announced” totalling $150 million.

But neither the CEFC nor ARENA had funding cut in the 2022 budget, she said.

Parliament has repeatedly knocked back coalition government attempts to use the agencies to fund more contentious projects linked to gas and coal.

But so-called patent box arrangements announced in Tuesday’s budget will allow the government to legally support a wider range of low-emissions technologies through tax breaks.

Some $53.7 million over four years will be used to help develop Australian intellectual property, officials said.

“It’s just another string to the government’s bow to incentivise the private sector to invest in low-emissions technology,” according to Department of Industry, Science, Energy and Resources head David Fredericks.

The tax system is being used to send a “strong signal” to the private sector to invest in the technologies that will get Australia to net zero by 2050, he added.