U.K. Labour leader Jeremy Corbyn | Jack Taylor/Getty Images Corbyn: Labour to back Remain if UK holds new Brexit vote The opposition leader does not come to a decision on whether Labour would back a Brexit deal of its own.

LONDON — Labour leader Jeremy Corbyn announced on Tuesday that his party would back Remain in any referendum on a Conservative Brexit deal, heralding a major shift in policy.

After a shadow Cabinet meeting, Corbyn wrote to party members to spell out the plan following consultation with unions and policy officials.

“Whoever becomes the new prime minister should have the confidence to put their deal, or no deal, back to the people in a public vote," he wrote. “In those circumstances, I want to make it clear that Labour would campaign for Remain against either no deal or a Tory deal that does not protect the economy and jobs.”

Late Monday the bosses of 12 major trade unions agreed Labour should back Remain in a referendum on any Tory Brexit deal or no-deal departure — giving Corbyn the green light. In the event of a general election, the unions said, Labour should promise to renegotiate the Brexit deal and put it to a referendum, but the party should decide at the time whether to back its own deal or Remain in a public vote.

However, Labour's new policy does not cover any manifesto commitment — officials said it only covers the incoming Conservative prime minister.

The move is likely to buoy Labour members and MPs calling for a second EU referendum, while angering Labour MPs in pro-Leave seats who want Brexit delivered.

Former Labour MP Chuka Umunna, now a member of the anti-Brexit Liberal Democrats, accused Corbyn of "yet another fudge." He said on Twitter the Labour leadership wants to "keep open the door to standing on a pro-Brexit platform in a General Election or supporting it in government."