On the Sunday night of Labour conference, one rally is expected to attract the biggest crowd of the season. Its theme is a subject that was once deemed one of the most difficult in politics – yimbyism. Yimby stands for “yes in my back yard” – a play on the traditional nimbys, who have been a dominant force in British politics where planning has been one of the thorniest battlefields. It is a campaign for more housebuilding, more turbines, more infrastructure, even on once-sacred spaces such as the green belt. For many of the most ambitious of the new cohort of Labour MPs, this is the fashionable campaign of the moment, not for economic growth but as a social justice movement – and one that many of the new millennials entering parliament hope to stake their careers on. That is also in part down to the striking relative youth of the Labour MPs. Nine of them are under 30 and preliminary data based on the ages, where available, of the 2024 cohort shows the average age is 43. Yimbyism is a radical departure from the politics of the last parliament, where 107 Tory MPs on the Planning Concern Group successfully forced Michael Gove to abandon all mandatory housebuilding targets – though there are a minority of Tory yimbys waging that war within their own party. But for Labour in government, it is not just a dividing line with the Tories but also what it sees as its most powerful attack on the new electoral threat from the Greens. Political strategists plan to paint the Greens as local blockers to a raft of projects from electricity pylons to affordable housing. “Yes, this is a Tory dividing line, but where it is much more interesting is on the left,” one senior government source said. “It makes us the serious player, we are the only party who can do this.” “The yimby moment has come,” one MP declared, describing a Starmer-loyalist army of men and women in their 30s and 40s who have been at the sharp end of the housing crisis from rising rents and punishing mortgages. There is a strong feeling among the group that housing was one major issue on which the Blair and Brown governments did not deliver. Inside Labour it is not a left-right divide, but some of its champions are prepared for it to mean internal party conflict between those who are radicalised on the housing crisis, and more nervous colleagues in rural or suburban seats won for the first time by Labour who might be tempted to retreat into nimbyism on local issues as a way of trying to keep their seats. Yimbyism is a highly convenient cause for No 10, which has put planning reform at the forefront of the government’s growth agenda, and one that has some fervent backers in cabinet, such as Ed Miliband and Angela Rayner. Starmer said he would describe himself as a yimby, when asked by the BBC earlier this year. Rayner’s plans for planning reform explicitly tackle that most totemic of planning issues, the green belt, in guidelines saying that councils lacking enough brownfield sites will be expected to offer untouched plots for construction. Miliband, the “king yimby” of the cabinet, has already had heated exchanges with the Green co-leader Adrian Ramsay for his objections to electricity pylons. “Things being built is a visible and tangible sign of a serious government willing to make difficult decisions,” one cabinet source said. “It’s so clear we need to build more housing but it is also so clear we need to build more energy infrastructure, from both a climate point of view but also because so much of our infrastructure is reaching the end of its life cycle. Any government would need to build this infrastructure but you can make this a positive story.” Starmer is betting the house on planning reform delivering the growth needed to improve public services, claiming that every 100,000 homes built adds approximately 1% to GDP. Experts still differ on whether it would really lead to lower energy bills or house prices, with Ian Mulheirn, the economist and the Tony Blair Institute’s former executive director for UK policy and chief economist, often arguing that the housing crisis has mainly been provoked by low interest rates, not lack of supply. Labour yimbys say this has been disproved in recent years because house prices remained high as interest rates leapt. With a new cohort of MPs preaching the gospel of yimbyism with such fervour, there is already pressure on the government to go further and faster, especially on public investment in infrastructure. For MPs on the left of the party, there is also the deep concern that social housing is far less of a priority. The yimby groups are well organised. Some of the most ambitious members of the new intake, many of them handpicked for seats by the Labour leadership, are now part of two influential caucuses on housebuilding. The first is the 50-strong Labour Growth group of MPs, which has ties to the influential Labour Together thinktank and is fronted by the MPs Josh Simons, the former Labour Together director, Lucy Rigby, a former solicitor, and Torsten Bell, the former CEO of the Resolution Foundation thinktank. The other is Labour Yimby, a grassroots group started by activists, which drew a crowd for its first parliamentary reception and is backed by some of the most vociferous housing campaigners from the new intake: Milton Keynes North’s Chris Curtis and Chipping Barnet’s Dan Tomlinson. Allwon Tory-held seats where housing was explicitly on the ballot paper, against incumbents who ran on an anti-housing platform. It is this group that has a rally planned at Labour conference in one of its biggest venues, holding 500 activists and MPs. It is also a personal issue for a huge number of MPs. Curtis, 30, is yet to be able to buy his own home. “For too long, politicians have ducked the tough decisions on housebuilding because they believe it will deliver short-term political gain. But in the long term it has made us all worse off, pushed people into poverty and made it too tough for the next generation to get on the housing ladder,” he said. Tomlinson’s win in Chipping Barnet unseated Theresa Villiers, the former Conservative cabinet minister who had been the leader of the Planning Concern Group. “There’s a bunch of us in this new generation of MPs who haven’t had to hear about the housing crisis from our children and grandchildren but have lived it ourselves,” he said.