U.K. Prime Minister Boris Johnson's majority in the House of Commons fell to one seat after Liberal Democrats won a by-election in the constituency of Brecon and Radnorshire, Bloomberg News reported.
The news comes ahead of Johnson's proposed Brexit delivery Oct. 31, with or without a deal.
Liberal Democrat Jane Dodds beat Conservative Chris Davies, who was previously convicted for falsifying expense claims. Dodds plans to tell Johnson to rule out a no-deal Brexit, Bloomberg reported, citing her victory speech.
The ruling party now holds 320 seats, with 310 Conservative MPs and 10 Democratic Unionist Party MPs, while the opposition holds 319 votes, including 13 Liberal Democrats, Bloomberg added.
Johnson won the election July 23 by securing 92,153 votes in the Tory leadership ballot, in which nearly 160,000 party members took part, while rival Foreign Secretary Jeremy Hunt obtained 46,656 votes.
Liberal Democrats, who are against the U.K. leaving the European Union, on July 22 elected Jo Swinson as their new party leader. Swinson has vowed to continue to push back against Brexit.