Kemi Badenoch has promised to win back voters who have deserted the Conservatives after securing an historic victory in the party’s leadership contest.

The 44-year-old becomes the first black woman to lead a major political party in the UK.

She defeated fellow right-winger Robert Jenrick, 42, by 12,418 votes after a marathon contest to replace Rishi Sunak, who led the party to the biggest defeat in its history in July’s general election.

In her victory speech, Badenoch promised to “renew” the party and told cheering supporters it was “time to get down to business”.

Badenoch, who is the sixth Tory leader in less than nine years, now faces the task of uniting a fractured party and leading opposition to Sir Keir Starmer’s Labour government.

The Saffron Walden MP said the Conservatives need to “bring back” voters who abandoned them, adding: “Our party is critical to the success of our country.

“But to be heard, we have to be honest.”

The party must admit it “made mistakes” and “let standards slip” over the last 14 years in government, she said.

Badenoch chose not to set out detailed policies during her campaign, focusing instead on returning the Conservatives to “first principles”.

All eyes will now turn to who she appoints to her top team as she sets out the future shape of the party over the coming days.

She praised Jenrick despite a sometimes bruising campaign and hinted he may be offered a senior job, telling him “you have a key role in our party for years to come”.

Badenoch, who became an MP in 2017 after a career in banking and IT, has said she would offer jobs to all of the Tories who launched leadership bids in July.

But shadow home secretary James Cleverly, who came third in the race, has ruled himself out.

The BBC understands, Badenoch plans to reveal her shadow cabinet by Wednesday, ahead of the critical Budget vote and her debut clash with Sir Keir at Prime Minister’s Questions.

Jenrick did not speak to reporters after the result was announced, but on social media called on his supporters “to unite behind Kemi and take the fight to this disastrous Labour government”.

He also thanked “everyone who supported my vision for a Conservative Party rooted in the common ground of British politics”.

Badenoch got 53,806 votes to Jenrick’s 41,388 – making it the closest Tory leadership race of recent times.

Bob Blackman, who oversaw the election as chair of the Conservative 1922 Committee, revealed the party membership had shrunk to 132,000 – the lowest level on record and down 40,000 members since the last vote by members in 2022.

Badenoch was congratulated by several of her predecessors, including Sunak, who posted on social media: “I know that she will be a superb leader of our great party.”

Ex-prime minister Boris Johnson lauded Badenoch’s “courage and clarity” and said she “brings a much needed zing and zap to the Conservative Party”.

In a social media post, Prime Minister Sir Keir Starmer said “the first Black leader of a Westminster party is a proud moment for our country”.

He added: “I look forward to working with you and your party in the interests of the British people.”

But Labour Party chair Ellie Reeves said the Conservative leadership campaign showed the party had “learned nothing since the British people resoundingly rejected them in July”.

Lib Dem leader Sir Ed Davey also congratulated Badenoch, saying “the first Black leader of a major UK political party is a historic moment for the country”.

But Reform UK deputy leader Richard Tice called Badenoch “another in a long line of Tory politicians who say one thing and do another”.

In a statement, he said: “Kemi Badenoch was front and centre of a government that failed Britain.”

Over the 14-week campaign, the debate was dominated by immigration, the economy and how the Conservatives can rebuild trust with voters.

The party was reduced to a record low of 121 seats in the House of Commons at the general election, with under 24% of the vote.

It lost voters in all directions to Labour, the Liberal Democrats and Reform UK, with thousands of Conservative voters also choosing to stay at home on 4 July poll.

Badenoch’s appointment as Conservative leader comes several days after Labour outlined its first Budget in 14 years.

Writing in the Sunday Telegraph ahead of the Budget’s unveiling on Wednesday, Badenoch was critical of the chancellor’s plans, saying: “Rachel Reeves is conjuring up billions of pounds out of thin air to invest infrastructure.”

In response to the new Tory leader, Chancellor Rachel Reeves told the Observer: “If Kemi Badenoch opposes this Budget, then she has to tell the country if she opposes investment to cut waiting lists, investment to recruit teachers and investment to build critical infrastructure. Labour has made its choices, now the Tories need to make theirs.”

Badenoch told the Sunday Telegraph after her election on Saturday: “Labour are going to fail because they are repeating many of our mistakes and are doubling down on this broken system.”