Scott Morrison says he’s happy to work with the New South Wales government on its ambition to hit net zero emissions by 2050 because the premier, Gladys Berejiklian, “has a plan” – although the plan the prime minister referenced on Tuesday ends in 2030.

Despite blasting Labor federally for adopting the same net zero target as the Berejiklian government, the prime minister told parliament circumstances were different in NSW because there was a strategy in place to deliver a transition.

“We have a plan,” Morrison told parliament on Tuesday. “That’s what the leader of the opposition doesn’t understand. He doesn’t have a plan, he just has some sort of vague commitment to something 30 years from now.”

In declining to criticise NSW, while criticising Labor federally, Morrison cited a recent $2bn agreement his government signed with NSW as evidence there was a plan in the state. “Just a few weeks ago, the premier and I stood together and we agreed a plan, some $2bn, to invest in what is happening in New South Wales and in Australia, to achieve important targets,” the prime minister said.

But the text of the agreement says the memorandum of understanding between the two governments commences on the day of signing, which was 31 January 2020, and continues until 30 June 2030. The text does not purport to be an agreement covering actions to 2050, although it does reference the NSW commitment.

Morrison said on Tuesday the agreement with NSW was “about getting access to the gas that this country needs to ensure that we can firm up renewable investments in this country, which is at record levels, to put stability into our electricity grid”.

“The problem with what the Labor party is proposing with their 2050 commitment, net zero target of 2050, is they have no plan.”

While blasting Labor for adopting net zero, the government continues to leave its options open about whether to adopt a 2050 target down the track. Earlier in the day, the prime minister told colleagues in their weekly joint party room meeting it wasn’t about “being for or against the target”.

“I won’t commit to anything that I don’t know the cost of, if I don’t know the impact on jobs,” Morrison told colleagues. “The leader of the opposition has got no plan he has got no clue what the impact would be.”

Morrison also used a warning about the economic consequences of the rapidly-spreading coronavirus to criticise Labor for signing up to net zero. “Given the economic challenge, Labor’s reckless approach on the economy is particularly troubling, signing up to a target with no knowledge of what it would cost,” he said.

While the political focus remained on 2050, Labor on Tuesday signalled it would adopt a more ambitious emissions reduction target for 2030 than the Coalition’s. Labor took a 45% emissions reduction target by 2030 to the last federal election, and is yet to determine its new medium term target.

The process of revising the medium term target will be contentious in Labor ranks. The NSW right winger Joel Fitzgibbon has already argued publicly that the ALP should consider adopting a bipartisan position with the Coalition.

The shadow climate change minister, Mark Butler, has rejected Fitzgibbon’s proposition, and told reporters on Tuesday Labor would base all of its proposed emissions reduction targets, including a new medium-term target, on scientific advice.

He said the government’s 2030 target was consistent with 3C warming “which would be catastrophic for a vulnerable continent like Australia, and for the rest of the world”.

“That’s why we have consistently opposed Tony Abbott and now Scott Morrison’s target for 2030,” Butler said. “The government’s current target, we still don’t know where that came from.

“Tony Abbott plucked it out of the air. He’s never produced scientific evidence or modelling to show it’s consistent with what we need to do on climate change.

“That will be our approach though, to take scientific advice, to work with the community, to work with businesses, on a proper pathway to net-zero emissions by 2050.”