Labour must ensure that the 1.5m new homes it plans to build are low-carbon, and are built on brownfield land, or risk further damaging the UK’s already precarious natural environment, experts have warned. Keir Starmer made plans for new towns and a massive expansion of affordable housing one of the key planks of his appeal to the electorate in his speech to the Labour party conference in Liverpool on Tuesday. But the terms “climate”, “low carbon” and “net zero” were missing from the party’s announcements of “an immediate blitz of planning reform”. Campaigners and green groups broadly welcomed the proposals, but called for more detail on how Labour would ensure that the new developments – including the biggest expansion of “new towns” since the aftermath of the second world war – would minimise damage to nature, biodiversity and the climate. “There is an urgent need to build new houses, but we’re not going to help improve the lives of people by building poorly insulated, poorly constructed, expensive to run boxes in sterile estates devoid of nature,” warned Craig Bennett, chief executive of the Wildlife Trusts coalition of nature groups. He called for all new builds to be low-carbon from the outset. “It’s high time that all new homes came pre-loaded with a combination of solar panels, heat pumps, green roofs and swiftboxes [for migrating birds], and with good quality nature such as trees, wetlands and grassland meadows on the doorstep,” he said. A Labour spokesperson said the new houses would conform to the future homes standard the current government was considering, but it is unclear as yet what that would involve. The future homes standard has been repeatedly delayed by the Conservative government, and a consultation document is now not due out until the end of the year. Ministers have repeatedly resisted calls to stipulate that new houses must have solar panels. Last week, the Guardian revealed that housebuilders had reaped savings of at least £15bn from the government’s scrapping of low-carbon regulations, which have meant they do not need to bear the cost of equipping new homes with solar panels, heat pumps and high-grade insulation. The cost of retrofitting those homes, thought to number close to 1.5m, could run to as much as £45bn. Housebuilders are among the biggest donors to the Tory party. Labour did not reply when asked whether it would stipulate that the new homes must be fitted with solar panels, heat pumps and high-grade insulation, or whether they would be connected to the gas grid. Labour’s plans will include development on some areas currently designated as green belt, though the party declined to say how much. Tony Juniper, chief executive of Natural England, said existing safeguards for nature, which require developers to preserve habitats or create new ones and ensure sewage systems are not overloaded, should be kept. He said: “Meeting our targets for nature recovery while at the same time providing more homes is certainly possible to do, not least because of new tools such as biodiversity net gain, local nature recovery strategies, and nutrient neutrality. If we take an integrated approach, rather than one based on a binary choice between nature or homes, then great results can be achieved, for people and the natural world.” Labour has insisted that much of current green belt land is actually “grey” belt – that is, it has already been degraded through past development of various kinds, or that is close to infrastructure such as transport. Labour sources cited old car parks as examples of such land. Shaun Spiers, executive director of the Green Alliance thinktank, said this could be problematic. “[Starmer] should be careful not to presume that because a particular bit of land is run down, it should be developed. This gives an incentive to landowners to run down the green belt.” Some campaigners were concerned that Labour appeared to consider “scrubland” as potentially usable grey belt land, as scrub can provide important habitats for wildlife and plant species. CPRE, the countryside charity, added that it was more important to repurpose “brownfield” land, that has already been developed but is now sparsely occupied. Brownfield sites could provide 1.2m new homes, the group said. Roger Mortlock, chief executive of CPRE, said: “Before we start thinking about a new generation of new towns, we need to make sure we’ve exhausted the untapped potential of brownfield land. While sustainable development on brownfield land in the green belt can be part of the solution, we challenge the idea that grey belt land should include areas of scrubland that should be restored to enhance natural solutions to the climate crisis.”