Rebecca Long-Bailey has challenged Labour leadership rivals to pledge to keep the party’s policy on nationalisation.
The punchy intervention came as Ms Long-Bailey officially made it on to the Leadership contest ballot by securing the backing of the Fire Brigades Union (FBU).
As Shadow Business Secretary Ms Long Bailey was a firm supporter of Jeremy Corbyn’s policy of bringing rail, mail, energy and water supply into public ownership.
A frontrunner in the Labour leadership contest, Ms Long-Bailey is popular on the left of the party and has gained the support of pro-Corbyn campaign group Momentum.
“Members have a right to know exactly where candidates stand,” she said at a rally in Leeds.
“I want to be clear that I am fully committed to the pledges in our manifesto last year for public ownership of energy, water, rail and mail.
“Other candidates say they agree with the transformative programme, but now I’m calling for specific, concrete commitments you can trust.”
She added: “Nobody voted Conservative because we pledged to bring the railways back into public hands, take on rip off energy companies and fix our broken water systems.
“Under my leadership Labour will stand up to the rip off privatisers, and bring wealth and power back into public hands.”
Rival Keir Starmer is expected to outline his plans for common ownership of public services later in the campaign.
A spokesman said: “Keir supports expanding common ownership, whether by outright nationalisation or by other forms such as municipals, community organisations or co-operatives: all of which mean services are run for the public, not for shareholders.”
Lisa Nandy said she wanted to democratise – rather than nationalise – industries like energy, but she supports nationalising rail.
She told the Mirror: “It’s common sense to bring the railways and post office back into public ownership, but that shouldn’t be the limit of our ambition.
“We should be thinking creatively about community ownership, co-ops and municipal energy companies – that’s how you genuinely empower people.”
A Lisa Nandy-backing MP said: “Lisa has been calling for public ownership of mail, rail and energy, longer than Rebecca Long-Bailey has been a member of the Labour Party”
Before entering the leadership contest in December, Ms Nandy said: “If I’m honest, I think nationalising the energy companies is a waste of money.
“Disrupting them by setting up municipal energy companies [and] energy co-ops around the country is a much better route.”
Ms Long-Bailey can add the backing of the FBU that to endorsements from the Unite union, Bakers, Food and Allied Workers’ Union, 21 local parties and 33 MPs.
She thanked the unions who backed her and said: “As leader, I will unleash our movement, take power back from the gentlemen’s club of Westminster and build an aspirational socialism that speaks to people’s hopes and dreams.
“The general election result was devastating, but our policies are popular and it’s clear we must not return to the politics of the past.
“Members need a leader who sticks to their principles and has the record to prove it.
“It’s time for a new generation to step up and lead our party. Together we can rebuild trust in all of Labour’s heartlands, from Blyth Valley to Brixton, and win the next election.”
Only one candidate left in the contest, shadow foreign secretary Emily Thornberry, has yet to progress to the last round.
She has until February 14 to either win the nomination of three affiliate groups that match the 5% criteria, or by securing support from 33 constituency Labour Party (CLP) branches.
Lisa Nandy made the ballot last week, securing the backing of the National Union of Mineworkers, Chinese for Labour and the GMB.
She has seven local party nominations and the support of 31 MPs.
Some 40 constituency Labour parties will announce who they are nominating for the leadership tomorrow on what is being called “Super Thursday.”
Mr Starmer already has 32 endorsements from local parties, plus the backing of Unison, Usdaw and Community unions.
Securing the majority of the 40 on offer this week would cement his position as frontrunner, ahead of Ms Long-Bailey.