The prime minister called suggestions that the Conservatives are losing their Southern heartland voters “a bit peculiar, a bit bizarre”.
And he insisted: “I think there’s some misunderstanding about the planning reforms – even some wilful misunderstanding on the part of some of our opponents.
“What we want is sensible plans to allow development on brownfield sites. We’re not going to build on greenbelt sites, we’re not going to build all over the countryside.”
The triumphant Liberal Democrats have pointed to anger over the top-down planning changes as a key reason for the shock overturning of a 16,000 Tory majority in the true-blue Buckinghamshire constituency.
Some believe the shake-up – which critics say hands too much power to developers, undermining local democracy – may be dead in the water, with the government fearing a further backlash.
But Mr Johnson appeared to point to the construction of the HS2 high-speed rail line as the reason for his crushing defeat, referring to “particular circumstances there”.
And he defended the planning changes, claiming they are vital to enabling young people to get onto the housing ladder – something rejected by a recent Commons inquiry.
“The young people growing up in this country should have the chance of homeownership and that’s what we’re focusing on,” the prime minister said, on a college visit.
“I think it’s a great dream for young people in their 20s, 30s that they currently don’t have in the way that they perhaps had a few decades ago.
“And that’s something that we want to bring back, we want to make it easier. And that’s what we’re all about.”
Ed Davey, celebrating his party’s “best-ever by-election result”, called the planning controversy “symbolic” of the way Southern voters are being ignored by the Tories.
It would “give so much power to developers and take them away from communities and not result in the affordable housing people need”, the Lib Dem leader warned.
But the prime minister’s spokesman played down any immediate rethink, telling journalists: “I’m not aware of any planned changes.”
Speaking in Dewsbury, West Yorkshire, Mr Johnson also said he is “very confident” that the remaining coronavirus restrictions in England will be lifted on 19 July.
Again, calling it “a terminus date” he said: “I think that’s certainly what the data continues to indicate.”
Mr Johnson said: “I have complete confidence in Matt and indeed all of the government who have been dealing with Covid-19 during the pandemic.”