The fourth Conservative prime minister in six years will take office next week, facing a set of inflationary economic and social crises not seen since the 1970s.

Energy bills set to top £3,500 a year for the average household are forecast to push two-thirds into fuel poverty by January, while food prices have leapt at the fastest rate for more than a decade, adding nearly £500 and rising to the average annual grocery bill. Key workers are striking or mulling stoppages, and services from health to the courts are on the brink of collapse. Meanwhile, sewage is pouring into our rivers and beaches, a grim metaphor for the state of the nation taking tangible form.

Voices on the right of the Tory party have been quick to seize on the overlapping crises to argue for the final burial of the “green agenda” identified with David Cameron, Theresa May and Boris Johnson, and the legally binding target to reduce greenhouse gas emissions to net zero by 2050. David Frost, tipped for a senior role in a Liz Truss cabinet, has led a vigorous attack on net zero, blaming the policy for high energy prices, to applause from rightwing commentators. Get rid of the “green crap”, their argument runs, gas prices will fall, and ministers can concentrate on the really important stuff instead.

Yet to row back on net zero would be to abandon the best hope of dealing with the cost of living, longstanding advisers have warned. Far from being to blame for the energy bills crisis, net zero – which requires energy to be used more efficiently and generated from clean sources – is the way out of it, they argue.

John Gummer, a former Conservative environment minister and chair of the Committee on Climate Change (CCC), said: “What we have to do for net zero is what we have to do for the cost of living crisis. When people say we can’t afford net zero, we frankly can’t afford not to go for net zero.”

Ben Goldsmith, investor and a longstanding green Tory, chair of the Conservative Environment Network of more than 100 MPs, said: “With what’s happened on the cost of living across the board – gas, electricity, food, everything – we need to put the response to that on something of a war footing. And that means a war footing for the effort around energy efficiency and renewable energy.”

Of the multiple pressing crises facing the incoming prime minister, at least three have strong environmental components. Soaring energy bills require an overhaul of the UK’s failing, gas-dependent energy system, from leaky homes to ageing nuclear reactors; the cost of living crisis is also fuelled by rising food prices, spotlighting farm policies; and the sewage scandal springs from failures over two decades to take the concerns of environmentalists seriously.

Home insulation could cut heating bills by half, and heat pumps further reduce the UK’s reliance on expensive gas, as well as reducing greenhouse gas emissions.

The rate of home insulation halved last year after the abandonment of the botched green homes grant. That scheme, launched by Johnson under the slogan “build back greener” from the Covid-19 shock, aimed to insulate 600,000 homes but was scrapped in March 2021 after it achieved only 15,000.

Rishi Sunak as chancellor withdrew the expected green homes grant funding and it was not restored, leaving the UK without a nationwide scheme for home insulation for average households for nearly 18 months at a time of soaring energy prices. Sunak omitted to mention insulation in the early part of his campaign, but in recent weeks has begun to promise a programme for housing – but without detailing how it would work. Truss has largely avoided the topic, calling instead for an end to green levies, which she says would cut £153 from the average household energy bill, but would also cut the money available for retrofitting the poorest homes and put jobs at risk.

Ramping up renewable energy would also bring down energy prices, but both candidates have set firm against solar power and new onshore windfarms, the cheapest form of electricity generation. Their motivation appears to be appeasing the right wing of Conservative members, for whom planning laws have long been a hot button issue, but poll after poll shows the public at large support the construction of new renewables.

Gaining planning permission for solar farms is already hard – at least 23 have been blocked in the past 18 months, that could have reduced energy bills by £100m. Of renewable technologies, only offshore wind appears appealing to the candidates – as Truss recently boasted, the world’s biggest offshore windfarm is under construction off the Yorkshire coast.

High energy prices will not be brought down by investments in North Sea oil and gas or fracking, despite both candidates’ enthusiasm for drilling. New gasfields take years, sometimes decades, to come onstream and fracking, even if it could overcome local opposition, is also unlikely to produce significant quantities of gas any time soon.

Food prices are also driving up the cost of living. New trade barriers as a result of Brexit have caused a 6% increase in food prices in the UK, according to the London School of Economics, but neither candidate will admit that. Instead, any change of policy on food is likely to focus on trade and farm policy, and the danger is that the new prime minister could renege on reforms, begun under May and continued by Johnson, to replace farming subsidies based on the amount of land farmed with payments for measures that preserve soils, protect nature and nurture wildlife, a new system known as environmental land management contracts (Elms).

That would be unwise, according to Goldsmith, whose brother Zac is the climate change minister, raised to the peerage by Johnson. (Zac is now an enthusiastic supporter of Liz Truss, but Ben has declared for neither candidate.)

“Farmers need to trust Elms, and the government needs to stay on course,” he said. “We have to reward regenerative agriculture, restore nature, and rebut the suggestion that restoring nature and rebuilding soil will cost us in food security, when the exact opposite is true.”

As well as the overriding issues of the cost of living crisis, the new prime minister will face a series of key decisions on green policy. Ministers have several times delayed any pronouncement on the proposed new coalmine in Cumbria, now set for November; Lord Deben was to step down from the CCC in September but will stay on until June, leaving the appointment of his successor to the new leader; and under the Environment Act, new standards for air quality should be set this autumn, in a key test of whether the government is serious about retaining environmental safeguards post-Brexit.

Green campaigners fear that promises made during the campaign of a “bonfire of regulations” mean the opposite is true, and that vital protections for air, water, wildlife, and other aspects of the natural environment could be lost.

Whether the new prime minister’s deregulatory zeal extends to demolishing the UK’s green protections depend to a large extent on the ministerial appointments they make to the cabinet, and within Downing Street.

Shaun Spiers, the executive director of the Green Alliance thinktank, said: “The composition of No 10 is very important. If Truss comes in with a slimmed down No 10, or Lord Frost, that’s going to be very difficult. No 10 has been hugely important in driving the nature agenda up to now.”

Domestic crises will preoccupy the new premier, but foreign policy concerns are also pressing. After hosting the landmark Cop26 UN climate summit in Glasgow last November, the UK will be expected to pull out all the diplomatic stops to try to hold together the fragile consensus forged there, amid the geopolitical upheavals that have followed the Ukraine invasion. Alok Sharma, the cabinet minister who led the Glasgow summit, threatened in an interview with the Guardian to resign if the new prime minister failed to commit to a strong green agenda.

Many nations will also look to the UK for a leading role in biodiversity negotiations, called Cop15, aimed at halting the precipitous decline in species and the natural environment. “The UK has been a leader in allocating international funding for nature restoration in the poorest countries of the world,” says Ben Goldsmith. Yet Sunak as chancellor cut overseas aid and Truss as foreign minister slapped a more commercial focus on much of the remaining funds.

Within Johnson’s cabinet, neither Sunak nor Truss showed much green inclination. Sunak blocked green spending, while as trade secretary, Truss downplayed environmental aims in trade deals and played little role in Cop26. “Neither is known for their passion for nature, and neither has made their name as an environmental leader,” said Goldsmith. Nor has either made the environment a major plank of policy in the campaign.

Whoever wins will need to look much wider, and that is where green campaigners are pinning their hopes. Polls consistently show that voters do care about green issues, from the climate to the UK’s sewage-strewn beaches, dirty air and plastic-choked rivers. Rebecca Newsom, head of politics at Greenpeace UK, said: “These issues couldn’t be closer to home, there’s clear demand from voters wanting to see these things sorted and the next prime minister has to get a grip on them.”