Sparked by its narrow win in the Uxbridge and South Ruislip by-election - a battle fought and won by the Conservatives' opposition to London's Ultra Low Emission Zone (ULEZ) scheme - some in the party are calling for a rethink of their current climate commitments, while others demand the government stays on track with its pledges.

It now appears the former camp may have secured some wins, with the news Prime Minister Rishi Sunak is expected to ditch key climate policies in a speech later this afternoon.

After details were leaked to the press, Mr Sunak released a statement with a dig at his predecessors, saying: "For too many years politicians in governments of all stripes have not been honest about costs and trade offs. Instead they have taken the easy way out, saying we can have it all."

But he did not unveil what plans were going to be kept, and which would be thrown out.

"This realism doesn't mean losing our ambition or abandoning our commitments," said Mr Sunak. "Our politics must again put the long-term interests of our country before the short-term political needs of the moment."

So what are the current pledges from the government? And which could be facing either delays or the axe?

Reaching net zero by 2050

The overarching promise from the Conservative government was to ensure the UK reduced its greenhouse gas emissions by 100% from 1990 levels by 2050.

The measure was made law by Theresa May in the dying days of her premiership back in 2019 and it was backed by Boris Johnson throughout his time in Number 10.

But when Liz Truss entered Downing Street, she ordered a review into the target - though her stint ended before it came to pass - showing not everyone in the party was onboard.

Mr Sunak has insisted he is committed to the pledge.

But questions have been raised over whether the government is doing enough to even meet the target, with the Climate Change Committee warning progress had been "worryingly slow", and time is "very short" to correct the path.

Phasing out petrol and diesel cars by 2030

In 2020, then prime minister Mr Johnson made a commitment to ban the sale of new petrol and diesel cars in the UK after 2030 - bringing the target forward by 10 years.

The £12bn plan promised to accelerate the rollout of charge points for electric vehicles, as well as the development and mass production of electric vehicle batteries, in an attempt to lower emissions and clean up the air.

Number 10 was saying as recently as August that Mr Sunak was committed to the 2030 date, though they hinted the ban was to be kept under review to ensure the prime minister's promise to be "proportionate and pragmatic" with climate policies was kept.

Levelling Up Secretary Michael Gove also doubled down over the summer on keeping to the pledge, saying the target is "immoveable".

But Business Secretary Kemi Badenoch was understood to be pushing back on one element - fining car manufacturers if they don't meet the target of making at least 22% of the cars they sell electric by 2024.

Current rules would mean a company would be subject to a £15,000 fine for every vehicle that does not comply.

Now, that may be redundant, as the plan is among those expected to be delayed in Mr Sunak's speech - with the deadline falling back to 2035.

The warring factions of the Tory Party are battling over whether his would be the right decision, but what has been interesting is the reaction of the car industry, with Ford among those calling for the original target to be kept, saying it is "a vital catalyst to accelerate Ford into a cleaner future".

Energy efficient landlords

Another pledge made by Mr Johnson in 2020 was to ensure all private rented homes had an energy efficiency rating of C or better - where A is the best and G is the worst - by 2028.

While the plan could be costly for landlords, it would lead to a reduction in bills for many renters and stop leaky homes adding to emissions.

But this is one proposal that looks set to have a pin put in it.

Mr Gove, the former environment secretary who is now the minister in charge of housing, said back in July he wanted to see the government "relax the pace" of the 2028 deadline, adding: "We're asking too much too quickly".

But now it is on the list of policies that could go in its entirety, with reports no new energy efficiency rules for landlords or homeowners would be brought in.

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The future of boilers

Another target that may be pushed back is ensuring all new homes are built with an alternative to a gas boiler - such as a heat pump - after 2025.

The measure would not impact people who already have gas boilers in their homes, or stop them from replacing like for like, as it would only be a rule for developers building properties.

However, making the move would cut emissions from new buildings and again help towards hitting that net zero target.

The wider ambition for all new heating system installations to be low carbon by 2035 - accompanied by a pot of £450m to help with household grants - also looks set to be watered down.

Reports suggest a new target would be to phase out 80% of gas boiler installations by the same date.

The additional policy of banning all off-grid oil boilers by 2026 is also set to be delayed to 2035 - again with a depleted target of 80% being phased out.

Hydrogen levy

Another move that already appears to have been shelved is the introduction of an annual levy to cover the cost of producing low-carbon hydrogen, instead of using fossil fuels, for energy at home.

The fee - which was expected to cost households around £118 a year - was due to be added to bills in 2025, and would help cut emissions by cleaning up the energy market.

But former energy security secretary Grant Shapps - who was recently appointed defence secretary - made numerous protestations about the cost being borne by people rather than companies, and has pledged numerous times to find another way of funding the change.

What else could be for the chop?

According to the government leak - first reported by the BBC - Mr Sunak could also make a pledge not to introduce new taxes to discourage flying.

He is also thought to be considering promising no policies involving changes to people's diets and no schemes to promote carpooling.

What about the other parties?

When it comes to Labour, one of Sir Keir Starmer's missions for government is to "make Britain a green energy super power".

The party said, if it got into power, it would cut bills and increase energy security by making all electricity zero-carbon by 2030, and carry out upgrades to 19 million homes to make sure they are insulated.

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It would also create a new publicly owned company called GB Energy, tasked with championing clean energy, increasing jobs and building better supply chains.

But Labour has backtracked on its £28bn a year investment pledge to accelerate the shift towards net zero, with shadow chancellor Rachel Reeves blaming rising interest rates and the "damage" the Conservatives had done to the economy since the announcement was made.

The Liberal Democrats have a raft of green policy proposals, including upgrading insulation in all existing homes by 2030 and ensuring all new builds are "eco friendly".

Other measures include investing to get 80% of the UK's electricity from green energy by 2030, and creating a £20bn Clean Air Fund to create walking and cycling routes to schools, and investment in pollution-free public transport.