LONDON • On a day of humiliating setbacks, British Prime Minister Boris Johnson suffered a major defeat in Parliament on Tuesday night as rebellious lawmakers voted to seize control of the Brexit agenda, prompting the embattled prime minister to say he would call for a new general election.

The 328 to 301 vote, made possible by fellow Conservatives who turned their back on Johnson’s pleas and now face ejection from the party, cleared the way for his opponents to introduce a bill Wednesday that would seek to prevent Britain from leaving the European Union without a deal Oct. 31. It was a momentous day in Britain’s Parliament as the legislature rose up to successfully challenge the power of the prime minister over vital Brexit policy.

If Johnson enjoyed a brief honeymoon since taking power in July, it came to abrupt end Tuesday when he faced his first vote — and a startling defeat — in Parliament.

There is still no clarity about how and when Britain will leave the prosperous EU bloc as the torturous Brexit process nears a climax more than three years after the original vote to leave. A new election would set the stage for a brutal battle over whether voters favor a “no-deal” Brexit, more negotiations, or possibly a fresh referendum on the entire question of leaving the EU.

The cross-party rebels are fighting to prevent a “no-deal” Brexit because of fears it would gravely damage the economy and plunge Britain into a prolonged recession while also leading to possible medicine and food shortages.

The vote came hours after Johnson suffered a key defection from his party, costing him his working majority in Parliament.

Johnson and his backers say these fears are overblown and that voters who backed Brexit are demanding action, not more talk.

On a day of high drama and acerbic debate in the House of Commons, lawmakers returned from their summer recess to confront Johnson over his insistence that the U.K. leave the European Union on Oct. 31, even without a withdrawal agreement to cushion the economic blow. Many shouted, “Resign!”

A new election would take Britain’s future directly to the people for a third general election in four years.

It is not clear Johnson would immediately get the two-thirds majority in Parliament needed to call a fresh vote because opponents are wary he might postpone the election date until after Brexit has taken place, in effect ramming through a “no-deal” exit.

Britain’s Prime Minister Boris Johnson speaks Tuesday in the House of Commons in London.

the associated press