With only three months to go before the Cop26 climate conference in Glasgow, the prime minister wants to be seen as leading the way internationally on reaching net zero carbon emissions by 2050.

However, his ambitions have been stymied by his failure to publish a roadmap on how to achieve the cuts, and a vocal group on the right of his party has begun to undermine the target by questioning the high price to consumers – ignoring the costs of inaction.

After months of delay, the prime minister has been accused by Keir Starmer, the Labour leader, of being “missing in action” on tackling the climate emergency. But there are also those on the left pressing Labour and the Conservatives to take much bolder, more radical action to aim for net zero by 2030.

Ahead of the publication of the government’s long-awaited climate change strategy, these are the competing political factions trying to win out in the battle over net zero.

The blue environmentalists

The dominance of this tribe in the Conservative party has happened gradually over two years, with the rising influence of Boris Johnson’s wife, Carrie, a committed environmentalist, and her circle of eco-friendly Tories. “If you want to get on these days, you need to be seen as green,” says one Conservative MP who has joined the Conservative Environment Network – apparently out of both ambition and sympathy with its aims.

As a faction that also includes the environment minister Zac Goldsmith and Johnson’s father, Stanley, the environmentalist Tories are on board with tackling carbon emissions but they are just as likely to be heard campaigning on oceans, protecting animals, rewilding and reducing plastic waste.

Boris Johnson, once a sceptic about the climate crisis and ways of tackling it, has form for deriding renewables, such as claiming windfarms could not “pull the skin off a rice pudding”. As recently as 2015, he suggested the idea that the warming climate was caused by humanity was a “primitive fear … without foundation”. But since about 2016 he has talked more about the environment and started mentioning climate change more when he became foreign secretary.

As prime minister, he accepted Theresa May’s target of net zero by 2050 and later signed the UK up to reaching a 78% reduction by 2035. Those who know him say he views a successful Cop26 summit in Glasgow as a potential legacy achievement.

However, there is a frustration among those committed to tackling the climate emergency that the Tory environmentalists – Johnson included – rarely talk about it with enough urgency and the prime minister has failed to lead from the front on Cop26, leaving the negotiations to his envoy, Alok Sharma, and most of the public discussion to his climate spokesperson, Allegra Stratton. With No 10’s net zero strategy, plus those on heating, boilers and hydrogen, having been long delayed, he has been left open to accusations that detailed thinking and motivation is lacking.

His approach is backed in parliament, though, by the Conservative Environment Network, the caucus of more than 100 MPs, which is ever keen to point out that they are in the mainstream of the party when it comes to believing in a carbon neutral future. The group of backbenchers, including Sir Bernard Jenkin, Andrew Mitchell and Damian Green, argues the UK “must continue to lead the way not only in promoting adaptation but also in reducing greenhouse gas emissions”.

Chaired by Zac Goldsmith’s brother, Ben, with Stanley Johnson on the board, it is a sizeable and influential faction. But their language is far from being full of alarm, and the messaging is instead focused on the practical ways of meeting the 2050 pledge, with a series of “net zero champions” looking at different policy areas, from nature-based solutions, electric vehicles and renewables to green homes, sustainable agriculture and green steel.

The Tory cost-sceptics

A section of Conservatives in Westminster, as well as many party members, would not rank tackling the climate crisis as a major priority. Barely any parliamentarian will publicly deny climate breakdown is happening. But there are plenty prepared to chip away at the idea that it is possible to halt dangerous climate change, especially in the case of the former chancellor Nigel Lawson and his Global Warming Policy Foundation (GWPF). The group is widely seen as a bastion of climate science denial, undermining the push for net zero emissions by focusing on criticising the costs to consumers of taking action.

Steve Baker, the prominent Tory backbencher, recently declared he has become a trustee of the GWPF, writing of the “net zero fantasies” and “ruinous economic experiment when we can least afford it”. There is also a small group of Conservative MPs, led by Craig Mackinlay, who argue that voters in their seats will not be able to afford the price tag of net zero, with no discussion of the costs of doing nothing.

At the other end of the spectrum there are those fighting politically behind closed doors for delay to action on net zero emissions or watered down proposals. No ministers will admit to being climate change deniers – despite views from the likes of Jacob Rees-Mogg, the leader of the Commons, who has argued in favour of adaptation rather than mitigation and changes in behaviour, and David TC Davies, a minister in the Wales Office. But some are known to be opposing the costs and also cautious about lecturing people on what they regard as lifestyle choices, such as driving an electric car, cutting back on flying and eating less meat.

Rishi Sunak, the chancellor, is fully signed up to the net zero pledge and the Treasury’s interim strategy report has said it will create opportunities for green jobs and growth. “The transition on growth to 2050 is likely to be small compared to total growth over that period, and it could be slightly positive or slightly negative,” it said. However, Sunak has made it known that a major priority for him is making sure it is affordable for consumers and others have accused him of blocking funding for meeting the 2050 target while downgrading the rollout of green boilers.

The Labour net zero pragmatists

Starmer has said tackling the climate emergency is a “burning issue” for his leadership but he also leads the pack within Labour on pragmatism. His language is far more urgent and pressing than that of the government, explicitly referring to the climate emergency rather than change or crisis. He has also warned there is already “dystopia” caused by climate breakdown.

However, Labour’s official policy on climate change is only modestly more stretching than the official government target, aiming at substantially more than 70% reductions by 2030, compared with No 10’s aim of 68%. The agreed language is for the party to aim for “considerably above 70% as an absolute minimum – and as much as we could feasibly cut depending on the situation we inherit from the government previous government”.

Starmer is also reluctant to be specific about how people may have to adapt their lifestyles through eating less meat or taking fewer flights, saying only that “we are all going to have to adapt our behaviour”. With unions such as the GMB warning of the costs to industry and consumers of ditching gas boilers, Starmer has said he sympathises with those worried about the price and called on ministers to show leadership and figure out how to make the options affordable.

Some unions have been instrumental in watering down the party’s ambitions, with a compromise struck at party conference under Jeremy Corbyn’s leadership in 2019 to downgrade the target of net zero by 2030 to a pathway to net zero by that date, after they raised concerns about the risk to jobs and industry.

The Lib Dems support a more explicit trajectory than Labour, targeting 75% of emissions reductions by 2030 and net zero by 2045.

The climate emergency warriors

Many in the Labour party – often those on the left – as well as the Green party are warning that far more bold and radical action is needed to deal with the imminent emergency that the planet faces. At party conferences, there have been motions pushing for a “socialist green new deal” and some activists would still like to see a policy that enshrines a target of net zero by 2030. A campaign run by the group Labour for a Green New Deal has pushed for “nine concrete, radical changes” including a national food service and rapid phase-out of all fossil fuel. Their party conference motion this year will push for public ownership of industries including energy, water, transport, mail and telecommunications to aid the green transition – manifesto commitments from 2019.

Starmer is likely to feel the pressure from the left on the issue of net zero in particular, which is close to the heart of many activists. This wing of the party was sorely disappointed that Rebecca Long-Bailey, an architect of Corbyn’s green deal policies, was sacked as shadow business secretary. She was replaced by Ed Miliband, a former energy secretary in Gordon Brown’s government, who is an expert on the issues, but the policies have not yet gone far enough for the liking of many grassroots activists.

The Green party would like to target the UK reducing its own emissions to net zero by 2030 and seeking to reduce the emissions embedded in its imports to zero as soon as possible. The party – which will soon be under new leadership – is explicit about the need to reduce the demand for high-carbon consumption, including heating, travel and meat consumption, and recommends that UK policy should encourage small families.