The prime minister insisted he will "focus on the change that people want" after Reform won Labour-held Runcorn and Helsby in the by-election.
Nigel Farage’s party set a new record for the smallest majority at a parliamentary by-election since the end of the Second World War.
MP Sarah Pochin’s narrow victory saw Reform take a constituency which Labour won with a majority of almost 14,700 less than 12 months ago.
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