The House of Commons, she went on to say, was simply prevaricating.

“Do they want to leave the E.U. with a deal? Do they want to leave without a deal? Or do they not want to leave at all?” she asked. “So far, Parliament has done everything possible to avoid making a choice.”

Then she turned on her heel and stalked off.

It was an astonishing speech, first and foremost because Mrs. May desperately needs those lawmakers to vote for her plan next week. Her withdrawal agreement has been rejected twice: first on January 14 by a vote of 432 to 202; and then on March 12, by a vote of 391 to 242. She is struggling mightily, vote by intransigent vote, to cobble together a moderate majority to approve her plan before March 29.

This speech, to employ a bit of British understatement, did not help.

Over the hours that followed, lawmakers responded to the prime minister’s words with fury, saying she had intentionally stoked popular anger toward them. Supporters of remaining in the European Union, in particular, have felt vulnerable since 2016, when a far-right activist, agitated by the Brexit referendum, fatally shot a Labour lawmaker, Jo Cox.

“Democracy loses when a prime minister who has set herself against the House of Commons, then blames M.P.s for doing their job,” said a Conservative former minister, Sam Gyimah, who resigned from Mrs. May’s cabinet in November, saying he could not support her withdrawal agreement. On Twitter, he called her address “toxic.”