The double defeat showed a dramatic slump in support for the governing Conservatives, who have won the last four national votes, and suggests Labour is on course to win power for the first time since 2010 at an election expected next year.

While so-called by-elections are often lost by the governing party, the scale of the defeat in two parliamentary seats the Conservatives have held for years piles pressure on Sunak, who took over almost a year ago after the governing party became embroiled in scandals and chaos under previous leaders.

Starmer, who has moved his Labour Party closer to the center, said the two votes showed "Labour is back in the service of working people and redrawing the political map".

"Winning in these Tory [Conservative] strongholds shows that people overwhelmingly want change and they're ready to put their faith in our changed Labour Party to deliver it," he said in a statement.

Labour won the seat of Mid-Bedfordshire, an area about 80 kilometers north of London, overturning a majority of almost 25,000, making it the biggest deficit the party has overcome in a by-election since 1945.

Labour also overturned a large majority in another former Conservative stronghold, Tamworth, a largely rural constituency in central England, with the party enjoying the second-highest swing from Conservatives since World War II.

Many Conservatives had already resigned themselves to losing the two votes, blaming the former lawmakers for handing victory to Labour by the troubled circumstances of their resignations. But several said Sunak still had time to try to claw back the substantial lead Starmer's party enjoys in the opinion polls, but would have to make a bolder offer to voters.

The Conservative Party has only won one of the last 12 by-elections in this parliament, with half of the contests caused by resignations of politicians for misconduct.

Greg Hands, the Conservatives' campaign chief, pointed to the low turnout, saying the Conservatives had to find a way to get their traditional supporters out to vote.

"I didn't see any enthusiasm for Labour," he said.

Sunak, a 43-year-old former investment banker, has tried to cast himself as a bold reformer, no longer the cautious technocrat who restored some of the UK's credibility after scandals and chaos forced his two predecessors from office.

But with voters angry over high inflation, economic stagnation and long waiting times to use the state-run health service, Sunak is running out of time and opportunities to close the gap on Labour, which has enjoyed a double-digit poll lead over the Conservatives for over a year.

In a speech at his party's conference this month, Sunak sought to cast himself as a tough decision maker who was focused on reviving the economy while meeting what he said were the public's demands of watering down steps to reach climate change targets and “stopping the boats” to tackle illegal immigration.

The domestic measures have so far failed to change the polls but Sunak will hope that he can establish himself as a statesman before the next election. He is now in the Middle East where he is encouraging countries to avoid a further escalation in the conflict between Israel and Hamas.

One Conservative lawmaker said Sunak, and his finance minister Jeremy Hunt, needed a "radical rethink", urging the government to offer tax cuts to win over voters.

The contests in Mid-Bedfordshire and Tamworth were caused by the high-profile resignations of politicians close to former Prime Minister Boris Johnson.

Former minister Nadine Dorries resigned in a row over her failure to secure a role in the upper chamber of parliament, while Chris Pincher resigned in Tamworth after he was suspended from parliament for groping men at a London club.

Labour won Dorries' seat, which the Conservatives had held since 1931, with a majority of over 1,100. In Tamworth, Labour candidate Sarah Edwards won with a majority of over 1,300.

Peter Kyle, a senior Labour lawmaker, said his party had delivered a "political earthquake".

Popular

PDI-P will likely be part of opposition: Ganjar

Indonesia one step from Olympics after beating South Korea

Bahlil leads task force to boost sugar, bioethanol production in Papua