The Liberal Democrats have won the Brecon and Radnorshire by-election – meaning Boris Johnson’s working majority in parliament has now fallen to just one.
The result in the mid-Wales constituency is a significant blow to the new Tory leader, his first major defeat as prime minister.
Jane Dodds, the Lib Dems’ leader in Wales, won with a majority of 1,425 votes, taking 13,826 (43.5%) to former Tory MP Chris Davies’ 12,401 (39%), after a by-election was triggered due to his conviction for submitting false expenses.
Labour, which narrowly avoided losing its deposit after securing just 1,680 votes (5.3%), were beaten into fourth place by the Brexit Party on 3,331 votes (10.5%).
The Tory loss will add to the new PM’s challenges to steer Brexit through parliament and may increase the chances of a snap general election.
After the result was announced, Ms Dodds said her first act as an MP would be to find Mr Johnson and tell him to rule out a no-deal Brexit.
She told Sky News: “I’m determined to find Mr Johnson, wherever he’s hiding and say ‘you’ve really got to listen to what this has said’.
“This has said that the people of Brecon and Radnorshire do not want a no-deal Brexit. We burst his bubble in the first week of his premiership and he has to listen to that.”
She called for a new referendum on the terms of Brexit, saying “any deal must have that deal on the ballot paper and that must go to the people”.
The PM now has the support of 319 MPs, including the DUP which props up his majority, while opposition parties have 318.
A Downing Street spokesperson said: “The result demonstrates that a vote for any party other than the Conservatives is a vote to delay or stop Brexit.
“The Brexit Party can’t deliver Brexit, the Lib Dems won’t deliver Brexit, so we end up with the paralysis voters are tired of and ultimately parties don’t get to choose which votes they respect and which votes they ignore.”
International Trade Secretary Liz Truss also dismissed claims a no-deal Brexit would be harder to force through with a slimmer majority in parliament.
“I don’t believe parliament can stop it,” she told Sky News.
Lib Dem leader Jo Swinson has hailed the result as a “superb victory”.
She told Sky News “anything is possible” and if a general election is called she would be “fighting to win” because “there is no limit to our ambition in this volatile political time”.
James Cleverly, chair of the Conservative Party, defended the defeat, claiming the “real lesson” was that a majority of voters backed Brexit-supporting parties.
While Labour leader Jeremy Corbyn said it was an “obviously disappointing” result and vowed to “continue to put forward our message of anti-austerity which is something the Lib Dems cannot do”.
The turnout for the Brecon and Radnorshire by-election was 59.72% – the highest for a by-election in the current parliament.
The vote was triggered when Mr Davies was ousted in a recall petition after he admitted submitting false invoices for expenses.
He pleaded guilty in March to submitting two false expenses invoices for nine photographs costing £700 to decorate his new office, and was fined £1,500, ordered to pay £2,500 towards legal costs and told to carry out 50 hours of community service.
Some 19% of the electorate voted for his recall, well above the 10% threshold required.
Despite this, the Conservatives selected Mr Davies to try to win the seat back.
Ms Dodds won the seat after Plaid Cymru and the Green Party decided not to contest the seat as part of a pro-Remain alliance.
She overhauled a Tory majority of 8,038 seats from the 2017 general election with a swing to the Lib Dems of 11.96%.
Plaid Cymru leader Adam Price said the “spirit of co-operation” between the pro-Remain parties had led to Ms Dodds’s election, as he called for a second referendum.
“But if the prime minister is intent on a general election, he should know that Plaid Cymru and the other pro-Remain parties are committed to cooperating so that we beat Brexit once and for all,” he added.