British Prime Minister Theresa May said Monday that preparations for a "no deal" Brexit would be stepped up, and that Parliament should prepare for a number of different outcomes.

The comments from the U.K. leader followed the abrupt resignation Monday of a key member of May's Cabinet, Foreign Secretary Boris Johnson. David Davis, the minister directly charged with handling Britain's exit from the European Union, resigned hours before.

May's critics seized on the dual departures to chastise May's handling of Brexit, and to suggest that her government is ill-suited to facilitate the complex disentanglement of two of the world's major economies.

The pound, which had erased its earlier gains against the dollar following Johnson's resignation, fell further after May's Brexit comments.

May and European Union leaders have been reluctant to address the possibility of the E.U. and the U.K. failing to reach an agreement on Britain's departure from the E.U. Failure to reach a deal could imperil the E.U.'s budget, as well as the rights of citizens in the U.K. and E.U. to live and travel away from home.

On Friday, May secured a victory over the fiercest euroskeptics in her Cabinet. May's government signed off on a plan for a so-called soft Brexit that would preserve many of the trade and regulatory ties between the E.U. and the U.K.

In a post Monday on Twitter, European Council President Donald Tusk said that, while politicians such as Johnson and Davis come and go, "the problems they have created for people remain."

"I can only regret that the idea of #Brexit has not left with Davis and Johnson. But...who knows," he wrote.

Tusk tweet

Tusk has argued in favor of a deal, saying the failure to reach an agreement would impact all Europeans. But he has argued that the worst consequences of a no deal scenario would fall on the British.