LONDON (AP) — British Labour Party leader Jeremy Corbyn is facing increasing pressure to change the party's Brexit stance ahead of a key speech on Britain's plan to leave the European Union.

More than 80 senior Labour Party figures signed a statement published Sunday in The Observer calling for Britain to remain in the EU's single market and the customs union after Brexit. The letter states that Britain's economy would be so damaged by leaving the EU that Labour would be unable to carry out its reforms if it comes to power.

It says: "For the sake of building a better Britain and safeguarding those our party was founded to protect, we must grab this chance before it is too late. We will never be forgiven if we fail to do so."