Labour’s Brexit policy descended into chaos after Sir Keir Starmer refused to back Tom Watson’s claim that the UK could permanently remain in the European Single Market.

Sir Keir said Labour wanted the UK to secure a “changed relationship with the Single Market” post-Brexit despite Mr Watson, the party’s deputy leader, having suggested Britain could keep its current trading arrangements with the bloc indefinitely.

Mr Watson said remaining part of the Single Market and Customs Union “might be a permanent outcome” of Brexit negotiations.

But Sir Keir appeared to distance himself from his fellow frontbencher as he insisted the claim needed to be put “in context”.

It came as Sir Keir also issued a fresh threat to Theresa May that Labour will seek to derail her Brexit Bill if the party’s concerns about the UK’s withdrawal from the EU are not listened to.