Polls have officially opened for the by-elections in Wakefield and in Tiverton and Honiton.
The two seats, in West Yorkshire and Devon, were won by the Conservatives in 2019.
Polling station for both by-elections will be open from 7am to 10pm on Thursday, with the results expected between 4am and 6am on Friday.
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Eight candidates will stand in the Tiverton and Honiton by-election and 15 will stand in the Wakefield by-election.
Tiverton and Honiton by-election candidates:
Jordan Donoghue-Morgan, Heritage Party
Andy Foan, Reform UK
Richard Foord, Liberal Democrats
Helen Hurford, Conservative and Unionist Party
Liz Pole, Labour Party
Frankie Rufolo, The For Britain Movement
Ben Walker, UK Independence Party (UKIP)
Gill Westcott, Green Party
Wakefield by-election candidates:
Nadeem Ahmed, Conservative Party
Akef Akbar, Independent
Paul Bickerdike, Christian Peoples Alliance
Mick Dodgson, Freedom Alliance. Real People. Real Alternative
Sir Archibald Stanton Earl 'Eaton, The Official Monster Raving Loony Party
Jayda Fransen, Independent
Jordan James Gaskell, UK Independence Party
David John Rowntree Herdson, Yorkshire Party
Therese Hirst, English Democrats
Christopher Richard Jones, Northern Independence Party
Simon Robert Lightwood, Labour Party
Jamie Luke Needle, Liberal Democrats
Ashley Theo Blue Routh, Green Party
Ashlea Simon, Britain First
Chris Walsh, Reform UK