Labour faces a hard road back in its former heartlands because the party’s decision to back a second referendum cemented a sense that it had stopped listening, the potential leadership candidate Lisa Nandy has argued.

Nandy, the Wigan MP who served in Jeremy Corbyn’s first shadow cabinet, said that offering a softer Brexit was the “only way that you would have prevented the scale of the collapse” in seats across the north, Midlands and Wales.

Speaking to the Guardian in a pub in Wigan, she said it was easy to blame Corbyn and believe that without him “everything will be resolved”.

But she said the party’s Brexit position was also responsible. “In all honesty, Brexit just played into the sense that we are adrift from communities like these, that we don’t speak for them, we don’t stand for them, we don’t understand them, and worse than that: we’re deeply disrespectful towards them. And that has been building for the last 15 to 20 years,” she said.

“It’s been a long time in the making, I hope it won’t take a long time to resolve. But it’s going to be a hard road back.”

Nandy is expected to enter the race to succeed Corbyn as Labour leader in the new year, with rivals likely to include Rebecca Long-Bailey, Keir Starmer, Emily Thornberry and Clive Lewis.

Starmer, Thornberry and Lewis were all advocates of a second Brexit referendum, and had declared publicly that they would campaign to remain in the EU.

But Nandy insisted the policy was a mistake. “Once we adopted the position of a second referendum, there were a lot of Labour candidates in seats that voted overwhelmingly to leave who knew that they didn’t stand a chance of winning the election,” she said.

“More importantly, [they] knew they didn’t stand the chance of getting a hearing or gaining the trust of the people in their own communities, including lifelong Labour voters who felt voting Labour was very much part of their identity. And the reason for that was because it was about respect.”

In scathing comments about the People’s Vote campaign, Nandy said: “Even the title of it, back home here [in Wigan], said to people that you’re not people – you’re the wrong people – and the wrong people voted, so we need to get the right people to vote.”

Facebook Twitter Pinterest Lisa Nandy stands up in the House of Commons earlier this week. Nandy said she was ‘seriously thinking’ about standing to be Labour leader. Photograph: UK Parliament/Jessica Taylor/PA

She added: “I suppose one of the great lessons there has to be for the Labour leadership, whoever that may be going forward, is that people are not stupid. They are much, much smarter than you think. And they understand what is happening. And if you say to them that this is simply a question of democracy, but the only right option is to remain, they can see right through that.”

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Nandy also echoed criticisms made by other leadership hopefuls about Labour’s manifesto, which she said included policies that did not seem relevant to people’s lives. She cited the free broadband policy, which she believes “missed the mark, for people who are struggling with so many other things in their daily lives at the moment”.

“I’ve got a lot of constituents here who have a pound left in their pocket at the end of the week. And actually, free bus travel would go a lot further than free broadband,” she said.

Nandy also said she thought Labour’s re-nationalisation agenda had gone too far. She said she backed the case for nationalising the railways but as a former shadow energy secretary believed there were better ways of improving the energy market than nationalising the gas and power utilities.

“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,” she said.

Nandy, who is “seriously thinking” about standing for the leadership, is considered to be on the soft left of the party and was cautious about being too critical of Corbyn or his supporters in Momentum.

Like Starmer, she said it was important not to “throw out everything that’s happened” since Corbyn became leader and to keep the “decisive break that we made in 2015, where we said that we will be much less cautious about state intervention, wearing our values on our sleeve and taking on what has long been held to be deeply unpopular issues like compassion towards refugees”.

But she said any new leader would have to confront the “devastating” impact of Labour’s failure to get to grips with the problem of antisemitism within its ranks, which had caused people to lose trust in the party.

Although she resigned from the shadow cabinet in 2016 and supported Owen Smith’s leadership bid against Corbyn, Nandy said she had only done so after going to see the leader with others from her wing of the party to try to find a compromise.

“One side had picked a fight and the other side was absolutely determined to fight it until one or the other and been smashed. And I could see where that was heading. You can’t win elections like that,” she said.

Nandy said that in 2010 she had been considered too leftwing to serve on Ed Miliband’s team but that it was not helpful to think of people as part of one faction or other. She said her own influences as a politician range from her Marxist father to her grandfather who was a Liberal MP, then peer.

Nandy, who wants to move Labour’s headquarters out of central London and its party conference out of cities, said devolving power to communities and local authorities was the only real way that people would feel they had control over their lives again.

“The only answer is to give communities power to make decisions for themselves,” she said, citing Greater Manchester mayor Andy Burnham’s free bus pass for older teenagers as a big success.

Nandy said the Vote Leave campaign’s “Take Back Control” slogan had “caught the mood in towns like Wigan, like no other slogan in our lifetimes” and “just really, really resonated with that sense that people had that they couldn’t shape the circumstances of their own lives”.

While the party tries to get back on track, Nandy said the important thing was for every part of Labour to come together and try to unite to thwart a hard Brexit.

“If that’s where we’re heading – and that is clearly where we’re heading – Labour needs to come together now,” she said. “Leave the culture war behind and start pulling together as a team to see if we can do whatever it takes with the cross-party working with the House of Lords making the case that out in the country, and to prevent the hard Brexit … When jobs start to go, people here will not thank us for having been complicit in a hard Brexit. So we’ve got to get out there and be vocal and see what we can do to protect people.”