France, May 7 -- Polls opened at 7am across Scotland, England and Wales in ballots that will be Starmer's biggest electoral test since his July 2024 general election landslide victory ended 14 years of Conservative rule.

Opinion polls predict grim results for Labour, which could amplify calls for Starmer, 63, to resign or face a long-rumoured party leadership challenge.

Nigel Farage's anti-immigration Reform UK and the left-wing Greens, led by self-described "eco-populist" Zack Polanski, are expected to be the main beneficiaries of widespread disillusionment.

"It's a huge barometer for how the country is feeling about this political establishment," said Melanie Garson, associate professor of politics at University College London.

"We'...