Rebecca Long Bailey has officially entered the race to be the next Labour Party leader.
The shadow business secretary, the favourite of the current leadership, is seen as one of the early favourites to succeed Jeremy Corbyn.
With nominations due to open on Tuesday, Long Bailey said the party needs a “proud socialist” to succeed Corbyn and said she could be trusted to maintain “our socialist agenda”.
Her comments will be seen as a thinly veiled swipe at shadow Brexit secretary Keir Starmer, who has been keen to stress his left-wing credentials despite being seen to come from a more centrist tradition.
Writing in the Tribune magazine, she said: “We need a proud socialist to lead the Labour Party, driven by their principles and an unwavering determination to see democratic socialism in our lifetime.
“For all of these reasons and more, I have decided to stand for election to become the next leader of our party.”
Meanwhile, party chairman and left-winger Ian Lavery formally announced he is not standing for the Labour leadership and will officially endorse Long Bailey.
“We must ensure that we never again are seen to be taking working class communities for granted or to write them off as ignorant or ill-educated,” he said in another apparent jibe at pro-Remain contenders.
Long Bailey’s announcement came as the party’s ruling National Executive Committee (NEC) set out the timetable for election, with the new leader to be announced at a conference on Saturday April 4.
Earlier, Angela Rayner threw her support behind Long Bailey, her friend and flatmate, as she officially launched her bid to become the deputy Labour leader.
Starmer has emerged as the early frontrunner in the race to succeed Corbyn.
Labour MPs Emily Thornberry, Jess Phillips, Lisa Nandy and Clive Lewis are also standing. Former cabinet minister Yvette Cooper has ruled out of a leadership bid.