On Thursday morning, Dominic Raab, the minister in charge of the Brexit negotiations, quit. “I regret to say that, following the Cabinet meeting yesterday on the Brexit deal, I must resign,” the Brexit secretary said in a letter to May. Two other ministers have also resigned.

Raab said he was leaving for two reasons. Firstly, the deal involves certain different regulations in Northern Ireland than in the rest of the U.K.—some goods coming into the British province from the rest of the U.K. would need to be checked for conformity with EU rules, for example.

This is to avoid a hard border between Northern Ireland and the Republic of Ireland, which is in the EU, but Raab said the agreement “presents a very real threat to the integrity of the United Kingdom.”

Secondly, Raab was displeased at the fact that the agreement’s backstop arrangement, which involves the U.K. and EU remaining in a customs union for an extendable transition period, cannot be unilaterally cancelled by the British. “No democratic nation has ever signed up to be bound by such an extensive regime, imposed externally without any democratic control over the laws to be applied, nor the ability to decide to exit the arrangement,” he wrote.

The pound fell sharply on the news of Raab’s resignation, from above $1.30 to below $1.29.

Raab, who the hardcore pro-Brexit wing of May’s Conservative Party see as a potential leader, was the second British minister to resign Thursday morning. The other was Northern Ireland minister Shailesh Vara, who cited similar reasons.

And after Raab came Esther McVey, the secretary of state for work and pensions, who said the deal would “bind the hands of not only this, but future governments in pursuing genuine free trade policies.” Then Suella Braverman, a minister in Raab’s Brexit department, and Anne-Marie Trevelyan, an aide in the education department. More resignations are likely.

Raab had been in the position for several months, following the resignation of David Davis—also an ardent Brexiteer—in July. Davis also believed the U.K. was conceding too much in its negotiations with the EU.

May will face members of Parliament later in the day, after which she is due to take questions from the press. The EU’s top Brexit negotiator, Michel Barnier, also has to sell the deal to the other 27 member states of the bloc.

It was already the case that the agreement, which pleases almost no-one, was unlikely to pass a vote in the House of Commons. Now, with Raab’s resignation, the chaos has only intensified.

This article was updated to reflect the resignations of Esther McVey, Suella Braverman and Anne-Marie Trevelyan.