The thumping victory set the tone for what will be a closely watched two days of results from elections for more than 2,000 seats on local authorities across England and a handful of high-profile mayoral elections, including in the capital, London.

The parliamentary seat for Blackpool South was up for grabs after the incumbent, elected in 2019 as a Conservative candidate, quit over a lobbying scandal.

Labour candidate Chris Webb won the seat with 10,825 votes. The Conservative candidate came second with 3,218.

While governing parties often struggle in local polls, the defeat in Blackpool and early signs of losses at the council level will boost Labour’s hopes for a sweeping victory over Prime Minister Rishi Sunak’s Conservatives in the national election.

“This seismic win in Blackpool South is the most important result today,” said Labour leader Keir Starmer.

“This is the one contest where voters had the chance to send a message to Rishi Sunak’s Conservatives directly, and that message is an overwhelming vote for change.”

Sunak’s Conservatives are about 20 percentage points behind Labour in most opinion polls for a national election, which Sunak intends to call in the second half of the year.