The Birmingham Yardley MP warned that the party will see more crushing defeats unless it recognises that politics has changed in a “fundamental way” and wins back the trust of its working-class base.
Ms Phillips, a frequent critic of Mr Corbyn and senior left-wing allies in his frontbench team, became the third candidate to formally announce their leadership bid following the party’s worst general election since 1935.
The Remain-backing MP said that voters have lost trust in Labour and stressed the need for the Prime Minister to be challenged with “passion, heart and precision”.
Among her criticisms of the party leadership were the “woeful response” to anti-Semitism in its ranks and for Mr Corbyn’s ambiguity on Brexit.
“We have got to be brave and bold and bring people with us, not try and look all ways. Trying to please everyone usually means we have pleased no one,” she said.
“Now is not the time to be meek. Boris Johnson needs to be challenged, with passion, heart and precision. We can beat him. We need to speak to people’s hearts, and people need to believe we really mean it when we do.” The MP, who worked for charity Women’s Aid supporting victims of domestic abuse before entering Parliament in 2015, said only “when we are clear and straightforward” will voters again back labour.
“We’re a party named after the working class who has lost huge parts of its working- class base. Unless we address that, we are in big trouble.”
On Saturday, she will meet former Labour voters in the Bury North constituency, which the party lost to the Tories. Ms Phillips also announced her candidacy on social media with a video in which she visited the north Wales constituency of Delyn that Labour lost to the Tories for the first time since 1987.
She joins shadow foreign secretary Emily Thornberry and shadow treasury minister Clive Lewis as those to have formally declared their bids. Others are expected to announce their intentions soon, with shadow Brexit secretary Sir Keir Starmer, Corbyn ally Rebecca Long-Bailey and Wigan MP Lisa Nandy considering challenges.
Ms Phillips came third in a YouGov survey of the membership behind Sir Keir and Ms Long-Bailey.