Kemi Badenoch has said it is “impossible” for the UK to meet its net zero target by 2050 – a goal set by a previous Conservative government.

The UK is legally committed to reaching net zero by 2050 under a law passed by Theresa May in 2019. It means the UK must cut carbon emissions until it removes as much as it produces, in line with the 2015 Paris Climate Agreement.

Badenoch said net zero cannot be achieved by 2050 “without a serious drop in our living standards or by bankrupting us”.

The Conservative leader did not set out a replacement for the target, but her words mark a sharp break from years of political consensus.

A source close to Badenoch said the Conservative leader still backs net zero, but not by 2050.

In a preview of a speech on Tuesday, Badenoch called lower energy costs and environmental protection “noble aims” but said current policies were “largely failing” to improve nature, while raising energy prices.

She said: “We’re falling between two stools – too high costs and too little progress.

“Net zero by 2050 is impossible.

“I don’t say that with pleasure. Or because I have some ideological desire to dismantle it – in fact, we must do what we can to improve our natural world.”

She will say she is not making a “moral judgment” on net zero or debating whether climate change exists.

But she said her Tory party is going to “deal with the reality” of the target, something she argues Labour and past Conservative governments ignored.

Badenoch’s speech kicks off a new chapter in her leadership, launching an overhaul of Conservative policies – starting with energy and net zero.

Badenoch won her party’s leadership on a promise to return the Conservatives to “first principles” before setting out detailed policies.

In her speech, Badenoch will announce details of a “policy renewal programme” – putting each of her shadow cabinet in charge of a policy area.

Badenoch’s comments come as governments worldwide are investing in renewables to meet international climate targets and lower carbon emissions to net zero by 2050.

The UN and Intergovernmental Panel on Climate Change (IPCC) have warned that global CO2 emissions must reach net zero by then to limit global temperature rises to 1.5C.

Target areas for cutting emissions include:

• reducing air travel
• minimising energy use
• improving home insulation and energy efficiency
• switching to electric vehicles
• replacing gas central heating with electric systems such as heat pumps
• cutting consumption of red meat

Labour is expanding renewable energy and said in its election manifesto it would invest £8.3bn in Great British Energy, a state-owned clean energy company, over five years.

Electricity is increasingly generated from renewable energy in the UK, and the cost of renewable generation has significantly fallen in the past decade.

Labour promised to bring down household energy bills by “up to £300 by 2030” – and Energy Secretary Ed Miliband has stood by the pledge.

But UK energy bills went up in January, and are expected to rise again in April.

The main reason for high energy prices in the UK has been an increase in the price of gas, which has been the largest source of fuel for years.

A Labour spokesperson said: “Kemi Badenoch claims she’s ready to ‘deal with reality’ while remaining in complete denial about the reality of the Tories’ appalling record in government.

“The Tory leader’s position is at odds with her own historic views. In government, she openly championed net zero.

“It’s clear the Conservatives stand for nothing and have learned absolutely no lessons. They haven’t changed.”

As a minister, Badenoch promoted the 2050 target as “crucial” to “achieve a cleaner, green future”.

Some Conservative voices criticised her latest move.

Sam Hall, Director of the Conservative Environment Network, called it a “mistake” and argued Badenoch’s speech “undermines the significant environmental legacy of successive Conservative governments”.

He said Badenoch was right to criticise Labour’s approach, but argued “the net zero target is driven not by optimism but by scientific reality; without it climate change impacts and costs will continue to worsen”.

But Lord Craig Mackinlay, a Conservative peer and net zero sceptic, praised Badenoch’s “reality check” on the 2050 target.

“Most of the world has already given up any pretence that it is affordable or achievable,” said Lord Mackinlay, founder of the Net Zero Scrutiny Group.

“Intermittent renewables that only stack up on the back of buckets of taxpayer cash are not the answer when we need cheap, reliable and secure energy.”

Her comments suggest she is not expecting to go as far as Reform UK, which has called for net zero targets to be scrapped in their entirety.

Last month, Reform UK deputy leader Richard Tice said his party “will scrap net stupid zero” if it won the next general election, and recover money paid in subsidies to wind and solar companies via a series of new taxes.