LONDON — Britain's main opposition Labour Party announced Tuesday it will reject Conservative Prime Minister Theresa May's proposed divorce deal with the European Union if it comes to a vote in Parliament and might even support a new Brexit referendum.

The party's chief Brexit spokesman accused May's government of offering the country a choice between "really bad and even worse."

If Britain and the EU agree on a deal, it must be approved by the British and European parliaments before Britain leaves. The math on the U.K. vote looks ominous for May's government, because it lacks an overall majority.

Brexit spokesman Keir Starmer told Labour's annual conference that the party would vote against a Brexit deal along the lines that May is proposing because it does not meet "six tests" it has set, including protecting workers' rights and retaining access to European markets.

"We do not accept that the choice is between whatever the prime minister manages to cobble together and no deal ... between really bad and even worse," Starmer said.

Starmer said if the British Parliament rejected the deal, there should be a national election.

"If that is not possible, we must have other options," he said. "Our options must include campaigning for a public vote — and nobody is ruling out 'remain' as an option."

Starmer's suggestion that a new referendum could reverse Britain's 2016 decision to leave the EU — which wasn't in the advanced printed text of his speech — drew a standing ovation from many delegates in the conference hall.

Labour party leader Jeremy Corbyn has long opposed the idea of a new Brexit referendum, saying the party must respect voters' decision to leave.

Most of the party's 500,000 members voted in 2016 to remain in the EU, but many of its 257 lawmakers represent areas that supported Brexit. Brendan Chilton of the pro-Brexit group Labour Leave argued Tuesday that the party would "hemorrhage votes" if it tried to stop Britain from leaving the 28-nation bloc.

But with Britain due to leave the EU on March 29 and negotiations at an impasse, Corbyn is under intense pressure from party members to support a new public vote.

With a show of hands, conference delegates voted Tuesday to back a compromise motion leaving the option of a second Brexit referendum open, but not calling for it directly.

EU leaders last week rejected the British government's blueprint for future trade ties at a fractious summit in the Austrian city of Salzburg.

May's plan seeks to keep the U.K. in the EU's vast single market for goods but not for services, in order to ensure free trade with the bloc and an open border between the U.K.'s Northern Ireland and EU member Ireland. But EU officials say that amounts to unacceptable "cherry-picking" of elements of membership in the bloc without accepting all the costs and responsibilities.

The Salzburg rebuff left May under siege from Brexit-supporting Conservatives, who want her to seek a looser relationship based on a bare-bones free trade agreement that would leave Britain free to strike new deals around the world.

But May is sticking by her proposal, saying the "hard Brexit" proposed by some Conservatives would be "a bad deal" because it would not resolve the Irish border problem.

"What we have put on the table is a good deal," she said Tuesday. "It's a deal which retains the union of the United Kingdom, our constitutional integrity, it's a deal that provides for no hard border between Ireland and Northern Ireland, protects jobs and enables us to have a good trading relationship with Europe and also the rest of the world."

German Chancellor Angela Merkel warned that time is tight. An EU summit next month is seen as a make-or-break moment for a Brexit deal.

Speaking in Berlin, Merkel said there were "six to eight weeks of very hard work in front of us in which we must take the political decisions."

"Of course, to a significant extent, this also depends on what Britain really wants — the discussion isn't so clear here," she said.