Sir Keir Starmer promised a new state-owned energy firm to help build a “fairer, greener, more dynamic nation” as he sought to present Labour as an alternative to “Tory failure”.

He said Liz Truss’s Government should not be forgiven for the market turmoil unleashed since Friday’s mini-budget, and promised Labour would “restore our sense of collective hope”.

But his attempts to portray the party as a government-in-waiting suffered a setback as MP Rupa Huq was suspended for describing Chancellor Kwasi Kwarteng as “superficially” black.

Sir Keir’s keynote address saw him tear into the Tories, saying they had crashed the economy to offer tax cuts for the richest 1% in society.

He said the Government had “lost control of the British economy” and “crashed the pound”.

He added: “Not for you. Not for working people. For tax cuts for the richest 1% in our society.

“Don’t forget. Don’t forgive.”

The Labour leader said the Tories “haven’t just failed to fix the roof, they’ve ripped out the foundations, smashed through the windows and now they’ve blown the doors off for good measure”.

A Labour government would “get us out of this endless cycle of crisis” with a “fresh start, a new set of priorities and a new way of governing”.

Painting himself as the successor to Clement Attlee, Harold Wilson and Sir Tony Blair, he said the party would “provide the leadership the country so desperately needs”.

“Because as in 1945, 1964 and 1997, this is a Labour moment,” he added.

Sir Keir said the war in Ukraine was not to blame for the way the Tories had left the UK unprepared for the economic fallout and the soaring energy bills faced by firms and families.

Labour would set up Great British Energy within its first year in office to “take advantage of the opportunities” in clean power in order to cut bills and generate a return for the nation.

He said: “The future wealth of this country is in our air, in our seas, in our skies. Britain should harness that wealth and share it with all.

“British power to the British people.”

The electricity generation company would be funded from the £8 billion National Wealth Fund already announced by Labour and would have operational independence, allowing it to invest in green energy schemes.

Sir Keir was scathing about the state of the nation after 12 years of Conservative rule.

The Conservatives had left a “Britain all at sea, where a cloud of anxiety hangs over working people”, he said.

“Lives are at risk this winter”, the Labour leader said, with the NHS “face down on the floor”, according to one medic he spoke to.

He claimed parents feared their children would not have the opportunity for a better life than them.

“That’s the deep cost of Tory failure. They keep talking about aspiration but they don’t understand how they’ve choked it off for working people,” he said.

Labour has been buoyed by opinion polls in recent days, with a YouGov survey suggesting the party has opened up a 17-point lead over the Conservatives, and Sir Keir stressed how much the party had changed under his leadership to make it “fit to serve our country” – in a swipe at Jeremy Corbyn’s record.

“That’s why we had to rip antisemitism out by its roots,” Sir Keir said.

“Why we had to show our support for Nato is non-negotiable. Show we want business to prosper. Shed unworkable policies.

“Country first, party second.”

He also sought to win back voters who had deserted Labour over Brexit – including those in the Red Wall seats in northern England who helped Boris Johnson secure his 2019 landslide.

“I want to speak directly to the people who left Labour on this issue. Whether you voted Leave or Remain, you’ve been let down,” he said.

“If you voted to take control of your life and for the next generation to have control of theirs, then I say to you: that is what I will deliver.”

He promised to help make sure “we buy, make and sell more in Britain”, to “control immigration using a points-based system” and “use the power of government to help working people succeed”.

“Labour will make Brexit work,” he promised.

Overturning the 80-seat majority won by Mr Johnson in 2019 is a tall order and Labour may be forced to rely on other parties for support in the event of a hung parliament.

But Sir Keir insisted he would not do a deal with Nicola Sturgeon’s Scottish National Party.

With the next election expected in 2024, Sir Keir warned “the next two years will be tough” with the Tories “getting desperate” and likely to “lash out”.

“We need to be prepared, disciplined, focused,” he told activists, adding that Labour should “meet their attacks with hope” and “provide the leadership this country so desperately needs”.

But in a sign that discipline may still be a problem, Ealing Central and Acton MP Ms Huq was forced to apologise to Mr Kwarteng for her “ill-judged” comments.

On a recording made at a fringe event she can be heard discussing Mr Kwarteng’s elite school background, before adding that “you wouldn’t know he is black” when listening to him on the radio.

Sir Keir’s speech was an attempt to show that the party is ready for power and Confederation of British Industries president Brian McBride said: “Against the backdrop of a cost-of-living crisis, it’s welcome to hear Labour re-state its pro-business credentials and double down on a commitment to sustainable growth.”

A Tory spokesman dismissed Sir Keir’s speech as “his 11th relaunch to date” and “full of vacuous slogans, rehashed phrases and empty promises”.