Twelve rebel Conservatives have signed an amendment calling for the U.K. to stay in the Europe Union’s single market, edging toward a common front with the main opposition Labour Party that could potentially force Theresa May to rewrite her Brexit strategy.

The move — less than 24 hours after Labour shifted its position toward keeping closer ties with the bloc — is a challenge to May’s pledge to withdraw from all EU structures in the name of reclaiming sovereignty, and could create chaos on the domestic political front.

May doesn’t have a majority, so even small rebellions can be enough to beat her. It’s still not clear whether Labour lawmakers and Conservative rebels will manage to orchestrate a defeat. Differences still remain as to just how close ties to Europe should be. Labour leader Jeremy Corbyn hasn’t embraced European Economic Area membership — full single market membership and keeping EU rules — as the Tory rebels have. But he gets very close with his call to remain in the single market.

The rebel Tories and Labour lawmakers appear to be sending signals to each other.

What Next For May?

May faces a marathon parliamentary voting session on Tuesday where her Brexit policy will be challenged. Parliament could make clear it wants a softer divorce If she gives in to rebels, she will almost certainly face a leadership challenge from the pro-Brexit faction of her party She’s also struggling to get her Cabinet united around a common Brexit position and negotiations in Brussels are stalled with just four months to go until both sides want an exit deal inked Whatever deal she negotiates has to come back to Parliament, so if lawmakers don’t assert themselves now, they will have another chance to force her hand in the Fall An early election is possible

Sending Signals

The Conservative rebels have proposed the amendment to the Trade Bill, a long-delayed piece of legislation for which no vote has yet been scheduled. It’s separate to the EU Withdrawal Bill, which has been heavily amended in the House of Lords and is coming back to the House of Commons next week for a 12-hour session in which the government will try to strip out all the Lords’ additions. The Labour Party on Tuesday proposed an amendment on the single market to the withdrawal bill.

There’s still time for more amendments to be added to the withdrawal bill, making for an even more perilous session on Tuesday.

Conservative lawmaker Stephen Hammond, who has signed the latest amendment, said he expects the long-delayed trade bill to come to parliament before the summer recess. Tories had been giving the prime minister “some breathing room,” but now they are pushing the government to “think again on this,” he said in an interview. He expects more Tories to sign the new amendment.

“This is about economic pragmatism; on day one after Brexit we need to have both customs and standards,” he told Bloomberg.

Labour lawmakers on the pro-EU wing of the party saw the Tory amendment as a signal to Corbyn that he could defeat May if he pushes his party to vote for full EEA membership.

“Wow. A dozen Tory MPs who support EEA Single Market have just tabled this pro EEA amendment to Trade Bill — they’re sending you a signal @jeremycorbyn,” Labour lawmaker Chris Leslie wrote on Twitter. “Are Labour frontbench really going to miss next week’s historic chance to defeat PM & prevent #Brexitausterity?”


Meanwhile, talks are going on in Brussels about what the future trading relationship between the U.K. and EU should look like. EU negotiators have long complained of the complicated domestic politics that make Britain’s stance hard to discern.

The move from the 12 rebel Tories comes just hours after the Labour leadership proposed an amendment to the withdrawal bill calling for single market membership. But the Labour proposal stops short of calling for full membership of the EEA.

The Tories’ trade amendment does call for EEA membership — which is single market membership and acceptance of EU rules, including those on free movement. It’s also known as the Norway model.

“If there was a free vote on the House of Commons on membership of the EEA, a majority of MPs would vote for it,” said Anna Soubry, one of the most high-profile Tory rebels. “My message to my colleagues is that it’s not enough to hide behind people like me. Your duty as an MP is to do the right thing.”

Pro-EU Labour lawmakers wanted Corbyn to go all out and call for EEA membership but he probably doesn’t have enough support in his party for that, as lawmakers from Leave-voting constituencies in particular object. Across the board there is concern that single market membership would be considered a sellout of the Brexit that people voted for in 2016, particularly as controlling immigration was a major factor in the referendum campaign.