The former Liberal party leader, John Hewson, has blasted “scaremongering” and opportunism in the climate policy debate, and warned that the Australian parliament faces one of its biggest deliberations since federation in choosing to unwind carbon pricing.

On Monday, the federal government is poised to push ahead with its promised repeal of Labor’s clean-energy package. All the relevant legislation required to scrap the carbon-pricing scheme and the various agencies – like the Climate Change Authority and the so-called green bank, the Clean Energy Finance Corporation – will be introduced to the lower house.

With only four parliamentary sitting days left until the new Senate takes it place on 1 July, the government is pitching past the current legislative deadlock on climate policy to the incoming Senate crossbench, where at least some elements of carbon repeal will get a positive hearing.

However, on Sunday Labor objected to the political focus being on carbon and mining-tax repeal when the government is unlikely to make several of its deadlines for various budget measures that are due to start on 1 July.

The opposition said the government’s approach towards the budget debate in this critical parliamentary sitting week was to stack separate proposals into single bills to avoid scrutiny, particularly in the welfare omnibus bills, and to crowd out the agenda with renewed parliamentary debates on carbon- and mining-tax repeals.

The Labor leader, Bill Shorten, said this was a deliberate attempt to avoid public debate on contentious savings’ measures that were ultimately worth billions of dollars. “They have deliberately bundled swathes of controversial budget measures into a small number of bills to hide from scrutiny,” Shorten said on Sunday.

While the government is busy ramping up its clean-energy repeal plans, advocates of carbon pricing are also intensifying their lobbying efforts before the Senate changeover.

On Sunday, Hewson said there should be a comprehensive process of Senate review to ensure the incoming crossbench fully understood the consequences of dismantling policies, implemented in the last parliament, to reduce carbon emissions.

The science indicated the world’s climate was “pretty close to a tipping point”, he said, and therefore substantial policy action had to be taken, and now, to avoid the dangerous effects of climate change.

“This is one of the most important parliamentary debates and parliamentary processes since federation. We can’t afford, as a nation, to get this wrong. It’s one of those things that should be fully debated, not just in the parliament, but beyond,” Hewson said.

He said the prime minister, Tony Abbott, had been motivated by short-term political opportunism, when in opposition, on the issue of carbon pricing – and that Labor had left a policy vacuum that allowed an old-fashioned scare campaign take root among voters.

Hewson said all parties should now come back to the table and work through sensible policy responses to global warming. He thought that elements of the Coalition’s direct action policy could work, but now was the time to have a “mature debate” about which policies were best to mitigate the risks.

As an economist, he said he was a long-time advocate of the market mechanism of carbon pricing.

Hewson was attending a Climate Institute function in Canberra. The institute’s chief executive, John Connor, said parliament should stick with the status quo. “The carbon laws are working. They are working to reduce pollution in a growing economy,” Connor said.