Coalition says Labor promises will be funded by ‘$387bn of new taxes on your income, your house, your savings’

The first costings war of the 2019 election campaign is underway, with the Morrison government releasing what it says are new Treasury numbers concluding Labor’s “tax hit on the economy” will be $387bn, not the $200bn figure it has been spruiking in its attack lines for months.

But the shadow treasurer, Chris Bowen, blasted back before the new material was published by news outlets, declaring on social media the calculations were “dodgy” and observing that “someone” in Treasury had some explaining to do, because the department has said previously it doesn’t cost opposition policies.

Chris Bowen (@Bowenchris) This is what ⁦@JoshFrydenberg⁩ has given out to media for publication tomorrow: dodgy “Treasury costings” of Labor policies. Given Treasury has said repeatedly they don’t cost Labor’s policies, someone’s got some explaining to do... pic.twitter.com/X7EaPrv3zJ

The material circulated by the government quantifies the cost of Labor’s decision not to proceed with stages two and three of the Coalition’s tax cuts, which deliver a tax cut to higher income earners – a decision confirmed by Bill Shorten during his budget reply speech.

The new figure puts the fiscal impact of Labor not proceeding with those tax cuts at $229.8bn, which is higher than a figure from the Parliamentary Budget Office of $226bn that Bowen shared during a speech to the National Press Club on Wednesday.

The Treasury costings also imply that Labor will collect less than planned from its signature housing tax policies to phase out negative gearing for existing dwellings and halve the capital gains tax concession. On Treasury’s figures, the measures will collect $31.5bn over 10 years compared with the PBO estimate of $35.1bn cited by Labor.

Stages two and three of the income tax cuts, opposed by Labor, would increase the threshold for the 19% tax bracket from $41,000 to $45,000 from 2022, then from 2024 flatten tax brackets so all taxpayers earning between $40,000 and $200,000 pay a marginal rate of 30%. Labor has derided the measure, which it says would see nurses paying the same marginal rate of tax as surgeons.

Both the PBO figure and the Treasury calculation also factor in the cost of Labor’s more generous low and middle-income tax offset, which benefits those earning less than $48,000.

Bowen said earlier this week that after four years, if Shorten prevails on 18 May, the tax to GDP ratio under Labor will be 24.2%. The Coalition has set a “speed limit” that taxes should not exceed 23.9%.

On Thursday night, Bowen said Labor was paying for new investments in schools and hospitals and “the biggest cancer care package in Australian history … by making multinationals pay the fair share and closing tax loopholes for the top end of town”.

Labor has been intensely critical of what it contends is a politicisation of the Treasury under the Coalition, particularly the appointment of Phil Gaetjens, a long-serving Liberal party staffer, to head the Treasury in 2018. Gaetjens failed to appear before a Senate estimates hearing this week, which prompted further criticism.

The treasurer, Josh Frydenberg, declared Labor promises would be funded “on the back of $387bn of new taxes on your income, your house, your savings and your super” – although that total is mostly due to Labor not matching a government income tax cut, and ending some existing concessions.

With the economy the focus of the Coalition’s early pitch in the election contest, Frydenberg said Australians could not afford Labor. “Bill Shorten’s taxes not only stifle aspiration but they will also hurt the economy, costing jobs and putting at risk the essential services Australians rely on.”

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The latest Guardian Essential poll, released at the start of the week, indicates the government’s recent budget was positively received by voters, although the government continues to trail Labor in the polls.

In terms of trust, the poll also indicates the Coalition maintains a clear lead over Labor when it comes to economic and budget management, and Labor maintains a clear lead over the Coalition on funding schools and hospitals, managing the economy in the interests of working people, and closing tax loopholes.

Scott Morrison opened the election campaign on Thursday by putting economic management at the centre of his re-election pitch, and warning if Australians made the wrong choice on 18 May they would be paying for it for the next decade.

Shorten countered that only Labor would make the economy deliver for workers on low and middle incomes.

The two leaders hit the hustings immediately after delivering their opening salvos, with Morrison touching down in the seat of Lindsay in western Sydney – a seat the government wants to take from Labor at this election, while Shorten campaigned in a government-held seat, Deakin, in Melbourne’s east, before relocating to Sydney.

The Liberal party also launched its first television advertisement, which focused on economic and fiscal management, warning voters now was not the time “to turn back”.