Former British Foreign Secretary David Miliband has joined with politicians from rival parties to call for Britain to retain the closest possible ties with the European Union after Brexit.

Miliband says the U.K. should stay in the European Economic Area, made up of the EU and countries such as Norway that have access to the bloc's single market.

Prime Minister Theresa May's government insists Britain will leave the EU's single market and customs union so it can strike new trade deals around the world.

But many businesses fear the economic harm of a hard Brexit. Miliband said Monday that staying in the EEA would provide "a safe harbor for Britain after Brexit."

Miliband joined former Liberal Democrat leader Nick Clegg and Conservative legislator Nicky Morgan to urge a soft Brexit.