LONDON         -     In a major blow to British Prime Minister Boris Johnson, UK lawmakers voted Saturday to postpone a decision on whether to back his Brexit deal with the European Union, throwing a wrench into government plans to leave the bloc at the end of this month.

At a special session of Parliament intended to ratify the deal, lawmakers voted 322-306 to withhold their approval on the Brexit deal until legislation to implement it has been passed.

The vote aims to ensure that the UK can’t crash out of the EU without a divorce deal on the scheduled Oct. 31 departure date. But it means Johnson must ask the EU to delay Britain’s departure, since Parliament previously passed a law compelling him to do that if a Brexit divorce deal were not passed by Saturday.

The government still hopes it can pass the needed legislation by the end of the month so the UK can leave on time. A defiant Johnson said after the vote that he was not “daunted or dismayed” by the result and would push ahead. He planned to introduce the Brexit-implementing legislation to Parliament on Monday.

He implied he would request a three-month delay as required but argued against any postponement.

“I will not negotiate a delay with the EU and neither does the law compel me to do so,” Johnson said. “I will tell our friends and colleagues in the EU exactly what I’ve told everyone in the last 88 days that I’ve served as prime minister: that further delay would be bad for this country, bad for the European Union and bad for democracy.”

Opposition lawmakers warned that Johnson must ask for the extension or face legal consequences. “Any failure of a prime minister who thinks he is above the law — well, prime minister, you’ll find yourself in court,” said Ian Blackford of the Scottish National Party.

Parliament’s first weekend sitting since the Falklands War of 1982 had been dubbed “Super Saturday.” It looked set to bring Britain’s Brexit saga to a head, more than three years after the country’s divisive decision to leave the EU.

Johnson implored legislators to ratify the deal he struck this week with the bloc’s 27 other leaders. He said members of the House of Commons should “come together as democrats to end this debilitating feud” over Brexit, which has bitterly divided the country since British voters narrowly chose in a 2016 vote to leave the EU. “Now is the time for this great House of Commons to come together ... as I believe people at home are hoping and expecting,” Johnson told lawmakers.

But he did not get the result he sought. Trouble began when House of Commons Speaker John Bercow said he would first allow a vote on an amendment that puts the vote on the deal off until another day. The amendment makes support for the deal conditional on the legislation to implement it being passed by Parliament, something that could take several days or weeks. It also gives lawmakers another chance to scrutinize — and possibly change— the Brexit departure terms while the legislation is passing through Parliament.

Johnson called any delay to Britain’s Brexit departure date “pointless, expensive and deeply corrosive of public trust.” And he warned Saturday that the bloc’s approval could not be guaranteed. “There is very little appetite among our friends in the EU for this business to be protracted by one extra day,” Johnson said.