Boris Johnson blasted Prime Minister Theresa May’s compromise plan for Britain’s exit from the European Union in a resignation speech in Parliament on Wednesday, claiming her proposal would leave Britain in “miserable, permanent limbo.”

Johnson, a Conservative member of Parliament and rival of May’s who quit as foreign secretary last week, urged the prime minister to push for a “strong, independent, self-governing Britain.”

“It is not too late to save Brexit. We have time in these negotiations. We have changed tack once, and we can change again,” he said. It is rare for ministers to deliver such a speech in Parliament.

Johnson was a leading Brexiteer in the 2016 E.U. referendum. He was also the face of Vote Leave — the official pro-Brexit campaign group that was recently fined for breaking electoral law by overspending almost $600,000.

When Johnson announced his intent to speak, some commentators wondered whether his address might be something akin to the 1990 resignation speech by Geoffrey Howe that preceded the downfall of Margaret Thatcher as prime minister.

In the end, Johnson’s speech didn’t appear to be the doomsday speech for May that some had feared. But it did underscore how bitterly divided Parliament is over Brexit and the type of relationship Britain wants with the E.U. after it leaves the bloc in March.

Johnson didn’t attack May directly — he noted her “courage and resilience.” His remarks are nonetheless a headache for the British leader, who is trying to rally support for her Brexit plan, which would see Britain remain closely aligned with the E.U. on trade rules for goods (though not services). Johnson said that May’s plan would mean that Britain would have “much less scope” to strike free trade deals around the world.

The latest squabbling over Brexit has renewed speculation about a possible leadership challenge for May, who has had a particularly rough few weeks with high-profile resignations, knife-edge votes in the House of Commons, and criticism of her Brexit plans from both those who want to remain in the European Union and those who want to leave.

But it’s unclear who would replace her. Johnson is widely considered to have leadership ambitions, yet he’s not as popular as he once was. He didn’t signal an imminent leadership challenge or call on May to resign on Wednesday.

During his speech, Johnson repeatedly praised May for her remarks at Lancaster House in early 2017, when she said that Britain would seek a clean break from the E.U. Johnson said that since then, Britain had “dithered” and “burned through negotiating capital” and allowed the Northern Irish border issue “to become so politically charged as to dominate the debate.”

In the past 18 months, Johnson said, “it is as though a fog of self-doubt has descended.”