Labour's failure to take Boris Johnson's former seat is a reminder that "policy matters", Sir Keir Starmer has mentioned - after the enlargement of the Ultra Low Emission Zone (ULEZ) by London mayor Sadiq Khan was blamed for the slim loss.
The opposition chief instructed activists that the Conservatives hanging on to Uxbridge and South Ruislip confirmed there was "never any reason to be complacent and never a reason to rest on our laurels".
It was additionally a reminder "there's still a long way to go", he warned - pointing on the market was "something very wrong" when a celebration coverage was on "each and every Tory leaflet".
Sir Keir has already urged Sadiq Khan to "reflect" on his ULEZ scheme, which is being held extensively answerable for lacking out on the west London constituency.
Mr Khan was standing by his plan on Friday, though mentioned he would monitor it.
The Conservatives clung on to Uxbridge by just a few hundred votes - massively down on the 7,210 majority that Mr Johnson received lower than 4 years in the past - tapping into anger over the move to extend the £12.50 daily charge on vehicles that don't meet emissions requirements.
Newly elected Conservative MP Steve Tuckwell's victory was the one piece of good news for Rishi Sunak after his social gathering misplaced the previous protected seats of Selby and Ainsty, and Somerton and Frome.
Addressing Labour's nationwide coverage discussion board in Nottingham, Sir Keir mentioned: "That result in Uxbridge demonstrates there is never any reason to be complacent and never a reason to rest on our laurels.
"It is reminder that in an election, coverage issues.
"We are doing something very wrong if policies put forward by the Labour Party end up on each and every Tory leaflet.
"We've acquired to resist that and to study the lesson."
Sir Keir also said Labour needed to show "historic ranges of effort, self-discipline and focus" as he warned of additional Conservative assaults within the wake of the Uxbridge by-election marketing campaign.
Read extra:Labour secure record win in Selby and AinstyLib Dems win Somerton and FromeConservatives hold Uxbridge and South Ruislip
In an obvious reference to a row this week over his refusal to scrap the two-child cap on benefits, he mentioned tackling little one poverty and social injustice can be a "massive part" of his mission for presidency - however commitments couldn't be unfunded.
Sir Keir mentioned: "We have to go about this step by step, shoulder to shoulder.
"It is a long-term venture, a venture that can solely be realised with credibility and self-discipline, that understands that spending commitments should all the time be funded.
"And because they must always be funded, that you can't just keep piling them on."
He added: "The Tories are watching us, looking for us to slip up.
"Make no mistake - they've given up on authorities, they have no report to defend.
"So next year, whenever that election comes, we know how they will fight it - that is the lesson of Uxbridge.
"All they'll do now could be oppose Labour, assault our plans, distract from their report.
"So we have to be ready in everything we do, starting today."
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