Local Labour members attended an online hustings meeting earlier today, and Ms Leadbeater was chosen from a shortlist of three candidates.
She said in a statement: “I am overwhelmed and humbled by the support and faith from members in Batley and Spen.
“I’m ready to hit the ground running and take Labour’s campaign to local people.”
During the online hustings meeting this afternoon, Ms Leadbeater made a passionate speech to Labour members.
She insisted she is “the candidate the Tories fear” because they know of her “proven track record of getting things done at a local level”.
Ms Leadbeater told Labour members: “I’m a proud Yorkshire woman and have lived in Batley and Spen all my life.
“I have a deep understanding of the area, its people and some of the challenges it faces. I feel passionately about the strength there is in such a diverse constituency.
“I’m the candidate the Tories fear.
“They know that I have a proven track record of getting things done at a local level and an established reputation for working for all parts of the community.
She added: “I have lived in almost every part of the constituency during my life – Heckmondwike, Batley, Cleckheaton, Gomersal, Liversedge, Staincliffe and Littletown – places candidates from other parties probably haven’t even heard of!
“We need strong northern voices at Westminster. People rooted in their communities. I will work to represent people across the whole constituency.
“Nobody should be in any doubt about the scale of the task we have to keep Batley and Spen Labour.
“The spotlight will be on us – but I want to show the world that both the Labour party in Batley and Spen and our community are strong and proud.”
The selection of Ms Leadbeater as the party’s candidate for the Batley and Spen by-election was welcomed by Sir Keir Starmer.
He said: “I am delighted that Kim has been selected to stand in the Batley and Spen by-election.
“Her roots in the community will make her a fantastic champion for Batley and Spen, tackling the issues local people are raising.
“Batley and Spen holds an important place in the Labour Party’s heart. And Kim’s work to bring people together, just as her sister Jo Cox did, has inspired us all.
“The people of the constituency know Kim well, admiring her hard work in the community and her determination to build a fairer, kinder society.
“I look forward to joining her on the campaign trail.”
The Batley and Spen by-election was triggered following a decision from Labour MP Tracy Brabin to quit Westminster following her election as the first mayor of West Yorkshire earlier this month.
The seat had been represented by Jo Cox until she was shot and stabbed by a far-right extremist in June 2016.
Labour and Sir Keir will be desperate for victory in the upcoming vote following a crushing defeat in the Hartlepool by-election, a seat it had held since 1974 when it was first introduced.
Ms Brabin has been Labour’s MP in Batley and Spen in West Yorkshire – like Hartlepool another marginal Red Wall seat – since 2016.
But after winning the West Yorkshire mayor contest, and with her new role including police and crime commissioner powers, she is not able to hold both roles at the same time, meaning a by-election will be triggered.
No date has been set for the contest so far although Labour, which will be defending a majority of 3,525 from the 2019 general election – could delay it until late July.
This is a breaking story. More to follow…