The U.K.'s opposition Labour Party wants Britain to stay in the European Union's single market for an extended period after it leaves the bloc, a shift in its position that could undermine Prime Minister Theresa May's efforts to deliver her vision of Brexit.
The proposal, which would mean no additional customs or migration controls in March 2019, would allow more time to finalize details of the U.K.'s departure and would give government and business time to prepare, said Labour's Brexit spokesman, Keir Starmer.
It would also eliminate the need to negotiate a transitional arrangement at the same time as a final deal.