A second poll shows the Coalition and the Labor party at level pegging on 50% of the two-party-preferred vote as Tony Abbott stirs backbench unrest and Malcolm Turnbull and his senior ministers struggle with their continued absence of a tax policy.

The Essential poll shows Labor’s primary vote on 38%, up three percentage points from the previous week – leaving Labor and the Coalition 50:50 after preferences.

The previous week’s Essential poll had the Coalition ahead 52% to 48% and this shift in sentiment is large for a poll based on a rolling average over the past two weeks. It comes after last Monday’s Newspoll, which also showed the parties at 50:50 on the two-party-preferred vote.

After weeks of backbench unrest over the Coalition’s consideration of a plan to limit negative gearing concessions, Abbott fuelled the dissent in the Coalition party room on Tuesday, arguing against the idea and demanding the Coalition fund any tax cuts by cutting government spending, as he had done in the 2014 budget.

His intervention came as the prime minister repeatedly refused to be drawn on the Coalition’s own negative gearing plans, and the finance minister, Mathias Cormann, refused on multiple occasions in one interview on Tuesday afternoon to repeat treasurer Scott Morrison’s view that there had been “excesses” in the use of negative gearing tax concessions.

“The treasurer can talk for himself, I am the finance minister, I look after the expenditure side of the budget,” Cormann said under questioning on Sky News.

“The treasurer speaks for himself. The treasurer is responsible for the tax system. The treasurer is also responsible for this process. I’m not going to give a running commentary on somebody else’s portfolio.”

When it ruled out an increase in the goods and services tax, after months of talking up the option, the government made it clear it was considering lowering superannuation concessional contributions and capping the amount that could be claimed through negative gearing deductions.

But for weeks conservative backbenchers have been publicly arguing against both propositions, and on Tuesday Abbott told the party room he agreed that negative gearing should not be pursued and the “only credible way to reduce taxes is to reduce spending”.

Abbott, who over the weekend wrote that he wore his 2014 budget as a “badge of honour”, claimed it was “time for the leadership to take on the savings challenge again”.

With defence spending effectively quarantined from cuts, focusing exclusively on spending cuts forces governments to trim health, education and welfare – the same areas Abbott hit in the 2014 budget, which was widely regarded as unfair. Closing or reducing tax concessions is a way of targeting savings at higher earners.

Treasurer Scott Morrison told the meeting the Coalition had very little room to move on tax policy because it had no budget surplus, and because even doing nothing was, in effect, taking a decision to see more salary earners move into higher taxation brackets.

“We have very few options,” he said. “It is like dancing on top of a pinhead.”

The Essential poll also shows health moving to the top of voters’ list of concerns. When asked to nominate their three areas of greatest concern, 43% nominated health, 37% economic management, 35% jobs and the protection of local industries and 29% ensuring the tax system was fair.

Turnbull has privately reassured state premiers his budget will contain interim funding to make up for $57bn in cuts to long-term hospital funding in Abbott’s 2014 budget. The interim funding would ensure hospitals could continue operation while longer-term changes to funding and efficiency are agreed.

The government is also struggling to get its deal on Senate voting reform debated in the Senate. Labor, which opposes the agreement, has filibustered for a day to prevent debate on the bill from even beginning.

The Coalition has the backing of the Greens for the changes, although there could be some last-minute amendments after Tuesday’s rushed Senate inquiry. The Greens have come under intense pressure because if the deal is passed into law by March, as the government is demanding, it opens the way for a July double-dissolution election.

The Essential poll showed voters back the Senate changes, with 53% saying they supported the reforms (including 52% of Labor voters) and only 16% disapproving. Thirty percent said they didn’t know.

During the party room discussion, Abbott described Turnbull’s attack against Labor’s negative gearing policy as “brilliant”, but said that was also a reason not to muddy the waters by the Coalition proposing negative gearing changes of its own.