After leaders of the European Union on Sunday unanimously approved British Prime Minister Theresa May's Brexit plan—which is the product of over a year of chaotic negotiations that saw key Tory cabinet ministers resign in protest—Labour leader Jeremy Corbyn immediately vowed to oppose the deal in Parliament, arguing it "gives us less say over our future, and puts jobs and living standards at risk."

"This is a bad deal for the country," Corbyn wrote on Facebook. "It is the result of a miserable failure of negotiation that leaves us with the worst of all worlds... That is why Labour will oppose this deal in parliament. We will work with others to block a no deal outcome, and ensure that Labour's alternative plan for a sensible deal to bring the country together is on the table."

Labour's alternative, Corbyn continued, "includes a permanent customs union with a U.K. say, a strong single market deal and guarantees on workers' rights, consumer, and environmental protections."

Labour's "six tests" for an acceptable Brexit agreement can be read here.

Now that EU leaders have approved May's Brexit deal, the agreement will be put before Parliament, where it is likely to face backlash from both sides of the political aisle.

With debate on the deal set to begin early next month, activists are already planning to flood the streets outside Parliament and demand that MPs vote down the agreement.

"Theresa May's Brexit deal is the worst of all worlds. When MPs debate the deal, let's protest outside Parliament—and demand they vote the deal down," reads one protest event page, which tentatively set demonstrations for Dec. 11.