Health chiefs, public sector unions and teaching leaders expressed horror on Saturday after the new chancellor, Jeremy Hunt, appeared to usher in a fresh era of austerity, and the threat of more misery for cash-strapped hospitals and schools.

In his first interviews since dramatically replacing Kwasi Kwarteng on Friday, Hunt provoked widespread alarm by promising “very difficult decisions” for government budgets.

The NHS Confederation, which represents the healthcare system in England, Wales and Northern Ireland, warned the prospect of further cuts was “incredibly grim”.

The head of the largest teaching union for England and Wales denounced Hunt’s attempt to placate the financial markets as “disastrous” and “scary” for schools, while another teaching union, NASUWT, said deeper cuts would cause “immeasurable damage to children’s learning”.

Meanwhile the GMB, which represents more than 500,00 public sector workers, said the Tories’ decade of austerity from 2010 scarred the country and stagnated the economy, adding: “The British people are being used as lab rats in a terrible Tory economic experiment.”

The TUC, whose 48 member unions represent 5.5 million workers, was equally outraged, warning that if Hunt’s approach took “an axe to vital services”, he would do as much harm to the UK as the widely derided chancellor he had replaced.

And Unison, which has 1.4 million members, called for an early election on the back of Hunt’s comments, stating it was “horrified that this is the government’s response to a crisis made in Downing Street”.

Appearing on Sky News in his first interview as chancellor, Hunt warned that “all government departments are going to have to find more efficiencies than they were planning”.

Even among his own party, the chancellor’s direction is likely to face significant opposition. Senior Tories were already cautioning that Hunt would struggle to secure enough parliamentary support for effective cuts to welfare, health or education.

The chancellor, they warn, will face as much opposition as Kwarteng would have done should he attempt to push through significant austerity measures.

Many MPs, including several in “red wall” seats in the Midlands and the north, are vowing to battle any attemptto cut promised infrastructure spending that is included in Hunt’s plans.

It means that while his pledge to reduce spending may appease the febrile markets, Hunt faces significant parliamentary barriers to implementing his medium-term fiscal plan, due to be unveiled at the end of the month.

“The difficulty he’s going to have is the same reason Truss said what she said on spending – she knew she couldn’t get it through the house,” said one senior MP. “I don’t think he’s any different in that respect. Who is going to vote for welfare cuts?”

Hunt’s cuts will arrive against a backdrop of soaring inflation and the cost of living crisis.

The Resolution Foundation thinktank calculates that about £20bn-£40bn of further fiscal restraint is probably required for debt to start falling.

Matthew Taylor, chief executive of the NHS Confederation, said that Hunt, a former health secretary, would be familiar with pressures on the organisation but warned of a funding gap that could reach £20bn by 2024-25.

“The prospect of further cuts and having to identify even more savings is incredibly grim. If that happens, with 132,000 vacancies, crumbling estates and soaring waiting lists, we are at a point where a serious conversation is needed about what the NHS can realistically and safely deliver. This is his [Hunt’s] moment of truth,” said Taylor.

Meanwhile, the education system is under similar duress. Kevin Courtney, joint general secretary of the National Education Union, the largest teachers’ trade union for England and Wales, said: “It’s really worrying. We need extra money in schools or there are going to be cuts: head teachers are going to be cutting support staff, cutting hours, asking parents for money for the basics of the school when parents haven’t got the money.

“That’s what we’re heading into, and the way Jeremy Hunt’s talking makes it all feel much more scary.”

Patrick Roach, NASUWT general secretary, added: “The system is already buckling and any further cuts would do untold damage to children’s futures.”

Frances O’Grady, TUC general secretary, said: “A responsible government would make it a top priority to rebuild our services after damage from the last decade of cuts and the pandemic.”

Unison general secretary Christina McAnea said: “No one voted for this. Essential services need investment, not another round of damaging cuts.

“An election is needed right away to put an end to this economic madness.”

Elsewhere, Gary Smith, GMB general secretary, added: “The Tories have trashed the economy – now they expect working people to pay the price once again.” Austerity cuts to the NHS, public health and social care from 2010 onwards killed tens of thousands more people in England than expected, York University research revealed last year.

Other effects included the closure of key council services, including hundreds of youth centres, libraries and subsidised bus routes.