U.K. Opposition Leader Jeremy Corbyn Backs EU Customs Union After Brexit

LONDON—Labour leader Jeremy Corbyn on Monday argued the U.K. should maintain close economic ties with the European Union while still influencing new EU trade deals, in a keynote speech that puts Prime Minister Theresa May in an uncomfortable position as she tries to sell her own Brexit vision to a divided Parliament.

Mr. Corbyn is hoping to undermine Mrs. May’s Brexit plans by attracting support from a small group of pro-EU Conservative lawmakers, deliver a parliamentary defeat and possibly precipitate an early election.