You don’t have to spend long in Westminster to see why politics is called showbusiness for ugly people. The grandeur of office may have faded, but the pomp and glamour of parliamentary power still confer celebrity on often unremarkable old men. Why anyone would want to be a local councillor, however, is more mysterious. Claire Kober became leader of Haringey at just 30, and has spent the past 10 years of her life in local government, forfeiting time with her two young children for interminable meetings about refuse collection policy. Most of us had never heard of her. Her resignation on Tuesday made headlines not because the nation is in thrall to local politics in her bit of north London, but because of what it may have revealed about Labour nationally. If Kober’s critics and supporters can agree on one thing, it would be that we may soon see what happened in Haringey repeated in constituencies across the country.

We meet at Kober’s home the next day, a lovely, big Victorian terrace in Muswell Hill, the leafier end of Haringey. She talks and moves quickly, and her briskness betrays the heightened tension of someone in the eye of a storm, but she is warm and broadly philosophical, and begins with the usual things people always say about what a privilege the job has been. A former charity worker, Kober, 39, took charge in Haringey in the wake of the Baby P scandal, and was widely praised for rescuing the council from crisis, for which she was awarded an OBE.

Then, after a pause: “I’m quite a practical, pragmatic person in all areas of my life. My politics are defined by an approach of: ‘Here’s a problem, let’s solve it.’ But we’re now in a political context that is much more ideological. And my politics aren’t the right politics for that time. So you’re either in denial about that, or you accept it, and say it’s time to move on.”

Late last summer Kober was taken aback to see Momentum members form slates and stand for “virtually every” position at the local party annual general meeting. She recalls the incumbent branch secretary defending her record, telling the meeting about all the hard work that she had done. “And then the other candidate for secretary got up and said, ‘I’ve not really been involved in the Labour party, I’ve been a member for a couple of years, haven’t really had the time, not really sure what the job entails, but I’d love to be secretary.’ And she won.”

Campaigners demonstrated last September against Kober’s proposed Haringey Development Vehicle in north London. Photograph: Alamy Stock Photo

Were alarm bells starting to ring? “I’m not naturally a worrier. I didn’t think, ‘Oh, this is terrible.’ I just thought selections would be more hard-fought than before. But I thought people’s records would speak for themselves.”

Since then, more than 20 sitting councillors have been replaced by Momentum candidates: five stood down, she says, due to the “toxic atmosphere”. With hindsight, does she think she was naive? “No.” She reconsiders. “Was I naive? I guess maybe I was naive about the changed political context. Yes, I was naive. I believed good people would win out. I thought their record would be how they were judged.” She doesn’t like to use the term “purge”, but “certainly what we’ve seen is an amazingly diverse bunch of people who did not deserve to lose their selections”. She mentions a young black man on the Broadwater Farm estate, and “an amazing woman who lives on a council estate, middle of Tottenham, runs the residents’ association, does everything, knows everyone”. It sounds as if she’s trying to refute the charge that her council was run by “zombie Blairites”.

“Yes.”

Kober’s opponents say the deselections had nothing to do with purging Blairites, and everything to do with housing. At the heart of the row is Kober’s £2bn policy, passed last summer, to sign a 20-year public-private partnership with a property developer called Lendlease, to redevelop and regenerate the borough’s estates and build 6,500 new homes. Critics of the Haringey Development Vehicle (HDV) fear it will knock down council tenants’ homes, drive them out of the borough, and build new luxury flats they can never afford to return to. Activists accuse Kober of “social cleansing”, and “pursuing a policy of Lebensraum”. Her eyes widen. “Which makes me a Nazi. That’s the climate in which politics is happening at the moment.” Last autumn, legal action against the HDV prompted a judicial review, and as relations within the party soured and grew ugly, the deselections began. Of the 28 sitting councillors who supported the HDV, only six have been reselected to stand in May, after which the newly elected council looks likely to be overwhelmingly opposed to the HDV.

Last July, her opponents tabled a council motion demanding Kober resign, then tried and failed to deselect her in November. When defeated, a local party meeting was convened to vote on a motion to abandon the HDV immediately. When that, too, was defeated, Labour’s National Executive Committee, was asked to intervene. Last week, the NEC instructed Kober to “pause” the policy.

Feelings have run high in the borough about the proposed private-public partnership with Lendlease. Photograph: Emerson Utracik/REX/Shutterstock

“The first I knew that it was going to be discussed at the NEC was when I got a text saying the meeting had started.” I think I detect a quaver in her voice. Was she angry? “Yeah. Local councils are elected by their local electorate, they’re not delegates of the national executive, and their autonomy is really, really important. We’re talking about a policy that is contentious, yes, but which has been consistently and democratically determined. No one was suggesting the NEC had to be involved because a rule had been broken. It was taken to the NEC because a group of people didn’t like the outcome of a recent meeting where it was decided to endorse the policy.”

Like almost every internal row since Jeremy Corbyn became leader, this one is framed on both sides by conflicting versions of democracy. Kober accuses the NEC of trampling over local democracy; her critics say it would be wilfully undemocratic to persist with a policy that is bitterly opposed by all the newly selected councillors who will be elected in May. “But in politics you don’t second guess the electorate. So we don’t know, actually, until the 3 May, what the electorate will decide.” As Haringey has almost always voted overwhelmingly Labour in every local election since 1968, I suggest this is conveniently disingenuous. “Yes, but there’s a principle at stake here. You’re elected for a four-year term, and you govern for a four-year term.” But is it democratic for councillors to lock the council into a 20-year policy abhorred by their successors? “I remain of the view if a vote is taken and a majority view reached, well, that’s the majority view, and you abide by it.” More to the point, she adds: “This is all hypothetical anyway.” Nothing can happen until the judge, who conducted a judicial review of the proposals last year, delivers his ruling, and chances are by then the council will be in pre-election purdah. “So what was the need for the NEC to intervene as it did?”

Why did Kober cite “sexism and bullying” in her resignation letter? “Well, I don’t think the argument that I’m incompetent would even have been marshalled if I was a man. Because I think it’s incredible – absolutely incredible. I almost wince in saying this, because I’m not trying to say I’m great, but I’m the chair of London Councils, I’m the most senior councillor in London, I lead on finance in the Local Government Association nationally, I’ve led a borough for 10 years – yet the national executive of my party has people in it saying I’m incompetent.” She’s sure this would not have been said to a man? “Utterly inconceivable. I cannot for the life of me, in any way, think a man would be bullied in that way.”

Kober admits the HDV plan was controversial … a protester at a demonstration in July 2017. Photograph: Emerson Utracik/REX/Shutterstock

I’m not convinced. Feelings about London’s housing crisis run so high, fuelled by Grenfell and Carillion, that I would guess a man trying to push through the HDV would have been similarly attacked. Local activist groups oppose the scheme; the local MP David Lammy is against it; Corbyn devoted much of his last conference speech to the scourge of “forced regeneration”. As Kober herself says, housing is the No 1 issue in Haringey.

“Look, we are in the grip of a housing crisis. What do we prioritise? Ideological purity – and accept that the consequence might be that we can’t build at anything like the scale we’d need to solve the problem? Or do we say: ‘Look, this is difficult, it’s complex, there are risks, but we have to try something else.’ Because what is the alternative? Do you just say we’re content to do nothing?” Presumably, I suggest, many in Momentum assume that soon Corbyn will be in power and passing laws that will let Haringey borrow enough money to build all the new homes it needs, without private partnership. “I would say you have a responsibility as a politician to engage with the world as it is, rather than how you wish it would be.”

The HDV commits Lendlease to make 40% of the new homes affordable. But similar promises have been broken in other developments, and London is littered with the failures of public-private partnerships. If we’re dealing with the world as it is, why should a council tenant in Tottenham trust yet another private developer to put the community’s interests before profits?

“So, the traditional way councils work with developers is the council procures a development partner and disposes of its land to that partner, and has to trust that it will deliver what they want. This isn’t that. It’s a joint venture. You’re retaining control with that 50%.” Are tenants guaranteed a right of return? “There are absolutely cast-iron legal agreements.” Can she see why they might not believe her? “I fully understand that. People who live on estates, in tower blocks, have often been failed by the state throughout their lives, in all kinds of ways. So, of course, people have the right to be cynical. But I get frustrated by elements in the community going round spreading misinformation and spreading fear. They’ve sent people letters saying you’ll be moved to Manchester and Birmingham. It’s totally untrue.” So why did the council’s own scrutiny committee call twice last year for the HDV to be halted? Kober looks suddenly tired.

Shadow chancellor John McDonnell attended the Haringey Labour party meeting held in December. Photograph: Richard Gardner/REX/Shutterstock

“Well, the scrutiny committee is chaired by the national vice-chair of Momentum.”

The HDV is almost unquestionably now finished. Come May, Kober will be gone. The question is whether Momentum’s victory in Haringey is a localised response to a specific policy, or a blueprint for future operations. What did Kober make of one council colleague’s suggestion that the HDV was just a trojan horse for Momentum? She hesitates. “You could quite convincingly argue that this is all about the HDV, and the trojan horse argument holds no water. If it weren’t for the fact that two months before the deselections, at the party AGM, Momentum stood against almost every officer in the ward – and that wasn’t about the HDV. Half of these people they targeted, I don’t even know their positions on the HDV, or whether they’d ever stated it publicly.”

I quote the MP Jess Phillips’ advice on how to handle Momentum: “Work now getting to know all the new members. You have to love them, rather than be scared of them, and if you love them they’re less likely to deselect you.” Kober lets out a hollow laugh.

“But that’s exactly what I used to say. I believe that in life, most things can work if you personalise and humanise and build relationships. But that’s not what happened.”

• This article was amended on 6 February 2018. An earlier version referred to the winning candidate for branch secretary at last summer’s local party annual general meeting as male. In fact that person was female.

