(CNN) Britain's pro-European Liberal Democrats have beaten the governing Conservatives in a special by-election, striking a major blow to Prime Minister Boris Johnson and reducing his already narrow working majority in Parliament to just one.

Liberal Democrat candidate Jane Dodds won in the Brecon and Radnorshire region of Wales, defeating Conservative candidate Chris Davies, who had previously held the seat.

The Conservative loss follows Johnson's pledge to take Britain out of the European Union by October 31 without a deal if necessary, and will likely be seized on by pro-European lawmakers as apparent proof that voters do not back his hardline stance.

"The people of this constituency have once again chosen hope over fear," Dodds said in a speech after the results were announced, calling the victory "a powerful message to Westminster."

"My very first act as your MP (member of Parliament) when I arrive in Westminster will be to find Mr. Boris Johnson, wherever he's hiding, and tell him loud and clear, 'Stop playing with the future of our communities and rule out a no-deal Brexit now.'"

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