UK Prime Minister Boris Johnson arrives for a meeting. File photo
The local election results will be seen as a barometer of support for Johnson's Conservatives nationally, as well as an indicator of whether the opposition Labour party poses a serious threat.
Johnson, 57, won a landslide general election victory in December 2019 on a promise to break years of political deadlock and deliver Brexit -- the country's divisive departure from the European Union.
But his position has looked increasingly fragile, because of damaging claims about lockdown-breaking parties at Downing Street and an inflationary surge that is squeezing voters' incomes.
A police investigation last month saw him become the first British prime minister to be fined for breaking the law while in office.
Irate Tory MPs, mindful of public outrage at double standards and denials, had looked set to force a no-confidence vote in his leadership in January.
But Russia's February invasion of Ukraine, during which Johnson has shown hawkish support for President Volodymyr Zelensky, took the heat out of any mutiny.