In the Uxbridge by-election, the Conservative Party narrowly retained Boris Johnson's former constituency, defeating Labour by a mere 495 votes.
The expansion of London's Ultra Low Emission Zone (Ulez), proposed by Labour mayor Sadiq Khan, was cited as a contributing factor to the Tory victory, The BBC reported.
The Ulez expansion, which is set to make the clean-air zone three times larger from August 29, has been a contentious issue in outer London areas, including Uxbridge and South Ruislip.
During the campaign, Labour's candidate Danny Beales called for a halt to the Ulez expansion, citing concerns about the cost-of-living crisis.
Following his win, Conservative candidate Steve Tuckwell attributed Labour's loss to Khan's "damaging and costly Ulez policy," asserting that it would burden residents financially.
"This wasn't the campaign Labour expected and Keir Starmer and his mayor Sadiq Khan need to sit up and listen to the Uxbridge and South Ruislip residents," he said.
Labour's deputy leader, Angela Rayner, acknowledged the need for clean air in cities but emphasised the importance of providing proper compensation and support to those affected by the policy.
"There is a concern that we have to make sure that whatever is implemented is not at the cost of working families," she said.
She pledged to work with Khan to develop a suitable scrappage scheme.
The Ultra Low Emission Zone was initially proposed by former Conservative mayor Boris Johnson in 2013 and implemented in central London in 2019.
Under Khan's administration, the zone was extended to include the area within the North and South Circular roads in 2021.
The latest expansion is set to encompass regions such as Buckinghamshire, Essex, Hertfordshire, Kent, and Surrey.
Drivers of vehicles that do not meet modern emission standards face a daily charge of £12.50 or a maximum £180 fine if they don't pay.
In the aftermath of the by-election, Labour leader Sir Keir Starmer avoided taking a definitive stance on the Ulez expansion, recognising both the mayor's obligation to reduce emissions and Beales’ concerns for potential constituents.
Conservative Party chairman Greg Hands accused Sir Starmer of flip-flopping on the issue, stating that the party defied the odds by retaining Uxbridge but faced losses in other constituencies due to Tory voters staying home.
In response to inquiries about the Conservative’s stance on green policies, Hands clarified that they were not opposed to such measures and emphasised the government's commitment to phasing out petrol cars by the year 2030.
Hands further explained that the government's approach involves allowing people sufficient time to make the transition to greener alternatives.
He contrasted this with Khan's implementation of the Ulez expansion, which he claimed gave people only nine months to comply with the new regulations.
The Uxbridge and South Ruislip by-election was triggered when Boris Johnson resigned as an MP last month.
Despite failing to win Uxbridge, Labour managed to make history by overturning its largest majority at a by-election since 1945 in Selby and Ainsty.
Meanwhile, the Liberal Democrats secured victory in the Somerton and Frome by-election with a significant margin of more than 11,000 votes.
