Labour should go into the next general election promising to rejoin the EU, Sadiq Khan has said.

The mayor of London has repeatedly made the case for joining the customs union and single market, but went much further on Wednesday night by suggesting the party should promise full membership at next ballot.

“We should, as a Labour party, fight the next general election with a clear manifesto commitment, a vote for Labour means we would rejoin the European Union. I think it’s inevitable,” he told the Italian publication La Repubblica.

Khan cited the time that had passed since the referendum and the economic instability caused by Donald Trump since Labour was elected in July 2024 as reasons why it would be desirable.

“President Trump is imposing tariffs to friend and foe, creating huge economic uncertainty that was unforeseen at the last general election,” he said.

“[And] America is involved with Israel in a war in Iran, causing huge additional economic uncertainty, affecting the price of oil, affecting the cost of living. God knows what President Trump’s exit strategy is, what the endgame is.

“So the facts have changed. The evidence has changed, which is why this parliament, we should rejoin the customs union and single market. I’m quite clear.

“On the ballot paper of the next general election is a vote for Labour, a vote to rejoin the European Union, and we should be unequivocal about the benefits of the European [Union] because we’ve now seen the alternative.”

The UK voted to leave the EU in the 2016 referendum, when David Cameron was prime minister, with the UK completing its formal separation from the bloc in 2021.

Khan said he saw on a daily basis “the damage Brexit has done to not just London, but Londoners, the damage economically, socially and culturally”.

He cited new research conducted by the National Institute of Economic and Social Research and Goldman Sachs that suggested the UK economy would have grown by an additional 10% but for Brexit.

Khan’s demand goes far beyond the government’s policy position, which is focused on “resetting” relations with the EU. The chancellor, Rachel Reeves, said in a speech earlier this week that the UK should follow more of the EU’s rules to boost trade and reduce prices.

Reeves said Brexit had hit gross domestic product (GDP) by up to 8% and contributed to higher prices for businesses and consumers.

She insisted she was not trying to “turn back the clock” on Brexit but to build a “new and stable future relationship” with Brussels.