Brexit shadow secretary Sir Keir Starmer confirmed that he will be the next Labor leader – becoming the fifth parliamentarian to enter the race.
Sir Keir has ended weeks of speculation with the announcement and will launch his leadership bid on Sunday at Stevenage.
He was a vocal advocate for Remain during his time as a deputy and chose the city of Hertfordshire, which voted 59% to leave the EU, to start his campaign to succeed Jeremy Corbyn.
Corbyn said he would withdraw from the Labor Party after suffering his worst defeat in the general elections since 1935 in the December elections.
Sir Keir joins Lisa Nandy, Jess Philips, Clive Lewis and Emily Thornberry as the fifth member of parliament.
A survey by Sky News earlier this week indicated that Sir Keir would win the lead – defeating Rebecca Long-Bailey, who has yet to confirm whether she will run.
Work has to be & # 39; reliable force for good & # 39; – Starmer
Writing in the Sunday Mirror, Sir Keir said: "In the coming weeks, I look forward to returning to the campaign and talking to people across the country about how Labor can rebuild and win.
"Britain desperately needs a labor government. We need a labor government that gives people hope for a better future.
"However, that will only happen if the Labor Party listens to people about what needs to change and how we can restore confidence in our party as a force for good."
In his letter, he said he knew how much "labor supporters are suffering" and talked about "incalculable damage that Boris Johnson will do to our country over the next five years."
He went on to say that Labor must "rebuild and speed up", including restoring confidence in the party.
Sir Keir Restante's position has been blamed by some of Corbyn's allies for the party's disastrous election results, but he will urge members not to swerve right, saying that defending a "bold and radical" Labor government is so important as always.
The human rights lawyer, who was named Queen's advisor in 2002 and served as head of the Crown Prosecution Service, accepted the knighthood in 2014 and has been striving to dispel perceptions of privilege.
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But he cited his upbringing by his father, toolmaker and mother nurse in Southwark, South London, in defense of his working class roots. He was also named after Labor founder Keir Hardie.
He became deputy for Holborn and St Pancras in 2015.
In a campaign movie released on Saturday night, Sir Keir highlighted his work in Stephen Lawrence's campaign, with Baroness Lawrence calling him "instrumental" to get justice for his murdered son.
Rebecca Long-Bailey has not yet declared
Also noteworthy is his work with the National Miners Union and in the McLibel case against McDonald's.
Sir Keir's critics fear he is seen as too Londoner, but that does not appear to have affected his poll in December, which showed he would take the final round of voting with 61%.
Wigan Nandy MP began her campaign in her constituency on Saturday, calling for a change in Corbyn's approach.
She said: "We need a different kind of leadership that will help us take root back in every community in the UK, which will turn us back into a real movement and strength, driven from the start so that we can regain the trust of our people." people".
Clive Lewis is seen as the underdog in the leadership race
In the meantime, Philips visited Bury North, which the Conservatives had chosen in the December 12 elections, to meet former party supporters.
Senior Labor MP David Lammy responded to numerous calls to run for the leadership campaign by excluding himself, suggesting that he was not the person joining the "vociferous factions."