Britain’s governing Conservative Party, which is trailing badly in the opinion polls, lost one of its safest parliamentary seats on Friday in a significant new setback for the prime minister, Rishi Sunak, who was also awaiting the result of another closely watched contest.
Voting in the two Conservative strongholds of Tamworth and Mid Bedfordshire took place on Thursday to replace two of the party’s lawmakers — one of whom quit after an allegation of sexual assault — and came as Britain’s health care system faces acute strain and its economy stagnates amid high inflation.
The first result, announced early Friday, from Tamworth, is a stinging blow to Mr. Sunak, who, since he became prime minister last year following the brief and disastrous leadership of Liz Truss, has failed to close a persistent double-digit deficit in the opinion polls against the opposition Labour Party. The stakes are high because Mr. Sunak must call a general election within the next 15 months.
In Tamworth, northeast of Birmingham, the vote was to replace Chris Pincher, the former Conservative lawmaker who had represented the district. He resigned from Parliament after a drunken incident in which, it was alleged, he had groped two men. In the 2019 general election, Mr. Pincher won with a majority of 19,634. On Friday that was overturned when Sarah Edwards for Labour won 11,719 votes, and the Conservative candidate, Andrew Cooper, won 10,403.
“Tonight the people of Tamworth have voted for Labour’s positive vision and a fresh start,” Ms. Edwards told her cheering supporters after the result. “They have sent a clear message to Rishi Sunak and the Conservatives that they have had enough of this failed government.”
Keir Starmer, leader of the Labour Party, described the vote as “a phenomenal result that shows Labour is back in the service of working people and redrawing the political map.”
In a statement, he added: “To those who have given us their trust, and those considering doing so, Labour will spend every day acting in your interests and focused on your priorities. Labour will give Britain its future back.”
A result was also expected early Friday from the vote in Mid Bedfordshire, around 50 miles north of London, to replace Nadine Dorries, a former cabinet minister and prominent supporter of Boris Johnson, who quit as prime minister last year.
Analysts caution against over-interpreting the results of these types of local contests — known as by-elections — where there is no prospect of the result changing the government, and voters often cast their ballots to register a protest against the governing party. Less than 36 percent of registered voters turned out to vote in Tamworth; in Mid Bedfordshire the number was higher, at 44 percent.
Because the Conservatives won so convincingly at the last general election, in 2019, Labour still has an electoral mountain to climb if it is to win a clear majority the next time Britons are asked to decide who should govern them.
Yet, the scale of the switch of votes does not bode well for Mr. Sunak, suggesting that even some of his Conservative Party’s more secure strongholds are no longer impregnable.
Mr. Sunak was praised for restoring some measure of stability after Ms. Truss’s economic plans roiled the financial markets and she became the country’s shortest lived prime minister in history. But he has struggled to win over the British public after 13 years of Conservative government.
In recent weeks, Mr. Sunak has tried to seize the political initiative with a series of eye-catching decision: scaling back climate change targets, canceling the second phase of a high-speed rail project, announcing new measures to phase out the sale of cigarettes to young people and proposing a shake-up the high school examination system.
Little electoral reward appears to have flowed from these announcements, however, three of which were made at the Conservative Party’s annual conference in Manchester earlier this month.
That meeting was distracted by a high-profile appearance by Ms. Truss, and by scarcely concealed jockeying from those who see themselves as contenders for the party leadership, should the Conservatives lose the general election.
By contrast, Labour’s conference in Liverpool, the week after, presented a more unified and confident image of a party that sees itself as close to power.
Friday’s results are the latest in a succession of election setbacks for Mr. Sunak. In July Labour won a by-election in Selby and Ainsty, in the north of England, overturning a Conservative majority of more than 20,000.
Earlier this month, Labour unseated the Scottish National Party from the Rutherglen and Hamilton West district, in a result that underscored a revival of the main opposition party’s fortunes in Scotland. Success there during the next general election could significantly improve Labour’s prospects of forming the next government.