Boris Johnson was under increased pressure to rethink his planning reforms as they were partly attributed to the Conservatives’ shock defeat in the Chesham and Amersham by-election.
Cabinet ministers were said to be among those warning the Prime Minister after the Liberal Democrats won the Buckinghamshire seat that has been a Tory stronghold since its creation in 1974.
The HS2 rail line being built through the constituency was a major issue in the campaign, as was the proposed planning reforms that have sparked fears about building in the countryside around the seat in the Chilterns.
Sir Ed Davey said his party’s victory would “send a shockwave through British politics” while claiming the result demonstrated that the “Blue Wall” of Tory southern seats could be vulnerable.
Mr Johnson conceded “it was certainly a disappointing result” when asked if he was neglecting voters in the South in favour of those in the North, but insisted: “We believe in uniting and levelling up within regions and across the country.”
Tory rebels were, in the wake of Thursday’s defeat, eyeing a chance to water down the planning proposals, with the legislation due to be introduced to the Commons.
Conservative Party co-chair Amanda Milling said the “concerns about planning and HS2 were loud and clear”.
“I am in no doubt that this result is a warning shot,” she wrote in the Telegraph, adding that “the people have spoken and we have heard them”.
Former environment secretary Theresa Villiers urged ministers “to use this as an opportunity to rethink their approach to planning reform”, while writing in the same newspaper.
“This by-election result should pave the way for a reduction in housing targets for the London suburbs and the South East,” she said.
“We need a fairer distribution of new homes across the country, rather than seeking to cram so many thousands more into the crowded South. There needs to be a stronger focus on brownfield sites in urban inner city areas.”
Tory MP for the Isle of Wight Bob Seely also said the Government “badly needs to think again about planning”.
“This entire system feeds the over-development of the South and the under-development of other areas. It needs to change,” he told the BBC.
The by-election was triggered by the death of former Cabinet minister Dame Cheryl Gillan who took the seat with a majority of 16,233 in the 2019 general election – some 55% of the vote.
But Lib Dem Sarah Green took 56.7% of the vote to secure a majority of 8,028 over the second-placed Tories.
Labour trailed the Greens in fourth place, winning just 622 votes and losing the party’s deposit in the process.
Polling expert Sir John Curtice told BBC Radio 4’s Today programme that he made it the “worst Labour performance in any by-election” after the party took just 1.6% of the vote.
One of Labour leader Sir Keir Starmer’s closest aides told staff he was standing down in the wake of the dire result.
Ben Nunn said he remained convinced that Sir Keir “will be a great prime minister” as he announced he was quitting as director of communications.