The health secretary, Matt Hancock, repeatedly urged fellow Conservative ministers to block a plan to build 400 homes and a primary school in his constituency, claiming it would damage the horse racing industry. His opposition to the development came as senior figures in horse racing leading the opposition made financial donations to him. Rachel Hood, the then Conservative mayor of Newmarket, and her husband, John Gosden, a prominent horseracing trainer who gave evidence opposing the scheme at the public inquiry, each gave Hancock £10,000 in December 2018 and May last year respectively. Tattersalls, the Newmarket-based racehorse valuers and auctioneers, who were also prominent opponents of the housing development on behalf of the racing industry, have consistently donated money to Hancock’s office, including £15,000 in May 2010 when he was first elected as MP for the West Suffolk constituency, and £10,000 in May last year. The development, proposed by the landowner Lord Derby at Hatchfield farm in Newmarket, includes building 400 homes, 30% of them affordable, a new primary school, and offices or other employment space. Commitments were given to manage any increase in traffic that might affect the movement of thoroughbred racehorses to their training gallops in the town, which is described as “the HQ” of flat racing. In July 2015 the scheme was recommended for approval by a planning inspector who decided after a public inquiry that “the risk to the horse racing industry is very small”. Two months later, Hancock wrote to the then housing minister, Brandon Lewis, maintaining that the development would damage the industry and should be rejected for its “exceptional negative economic impact on the local economy”. Sajid Javid, the then Conservative communities and local government secretary, blocked the project in August 2016. However, this was overturned by the high court in 2017, in a judgment that described Javid’s decision as “a complete and unexplained volte face” from a previous favourable government assessment of the plans, and noted the inspector’s finding that there was a clear need for more housing in Newmarket. Hancock nevertheless wrote to Javid after that judgment, again urging that the development be halted. He also wrote to the then housing minister James Brokenshire in July 2018, stressing his opposition to the scheme. After another public inquiry last year, in which the inspector again approved the development, Hancock wrote to the current communities secretary, Robert Jenrick, in September, attaching the legal case made by the horse racing industry to oppose the scheme. On 12 March, however, Jenrick accepted the inspector’s recommendation and finally approved the development. Hancock has accepted donations, including some hospitality, from senior figures in the horse racing industry since he was first elected MP, including badges and car passes for Newmarket races in 2010 and 2011 valued at just under £800, and in July 2010, honorary membership of the prestigious Jockey Club Rooms, worth £1,356. In August 2012, Hancock, a keen rider himself, won an amateur race in Newmarket on Dick Doughtywylie, a horse then owned by Hood and trained by Gosden. Hood marshalled the opposition on behalf of the horse racing industry to the Hatchfield farm development via the Save Historic Newmarket group, which she founded. On her register of interests at West Suffolk council, Hood also declares membership of the Racehorse Owners Association, Thoroughbred Breeders Association and Jockey Club Rooms. A spokesman for Hancock said he stood by his interventions in opposition to the development, and pointed out that he also received financial donations from a racehorse owner, Bill Gredley, who supported the scheme. Gredley told the Guardian he supported the scheme in a personal capacity, not representing the horse racing industry, because he felt “the people of Newmarket wanted some houses”. Tattersalls, also described in the high court judgment as having represented the horse racing industry at the planning inquiry, told the Guardian: “We have made donations either directly to our local MP or to the West Suffolk Conservative Association for the past 25 years … Our donations have never been related to any specific local issues, but have always reflected our support for our local MPs who we believe have historically represented the constituency extremely well.” Hood and Gosden did not respond to questions from the Guardian about their donations to Hancock. Claire Unwin, who unsuccessfully opposed Hancock for Labour in December’s general election, said: “The Hatchfield farm plans had very strong support in the local community because there is a great need for more homes, and affordable housing, so that people don’t have to move out of Newmarket. Matt Hancock was acting against the wider interests of the community and solely on the side of the horse racing industry, whose elite have been making financial donations to him.” The spokesman for Hancock, who has pointed out that all his financial donations are properly declared, said: “Matt is grateful for the Guardian highlighting how hard he campaigns for his constituency. He has opposed this development since before he was first elected MP. He is very grateful for all the support he receives from all quarters working hard for his constituency.”