British Prime Minister Boris Johnson's government on Thursday challenged opponents of Brexit in parliament to collapse the government or change the law if they wanted to thwart Britain's exit from the EU.

More than three years since the Brexit referendum, the UK is heading toward its gravest constitutional crisis in decades and a showdown with the EU over Brexit due in just 63 days' time.

In his boldest step since becoming prime minister last month, Johnson ­enraged opponents of a no-deal Brexit on Wednesday by ordering the ­suspension of parliament for almost a month.

The speaker of the lower house of parliament, John Bercow, said that was a constitutional outrage as it limited the time the 800-year-old heart of English democracy has to debate and shape the course of British history.

But Jacob Rees-Mogg, the Brexit supporter who is in charge of managing government business in parliament, dared opponents to do their worst.

"All these people who are wailing and gnashing of teeth know that there are two ways of doing what they want to do," Rees-Mogg told the BBC.

"One, is to change the government and the other is to change the law. If they do either of those that will then have an effect.

"If they don't have either the ­courage or the gumption to do either of those then we will leave on October 31 in ­accordance with the referendum result."

Johnson's move to suspend ­parliament for longer than usual at one of the most crucial junctures in ­recent British history was cheered by US ­President Donald Trump but provoked criticism from some British lawmakers and ­media.

Ruth Davidson quit as leader of the Conservative Party in Scotland on Thursday, saying she could no longer juggle the demands of being a mother with the balancing act of Brexit.

"I have attempted to chart a course for our party which recognizes and respects the referendum result, while seeking to maximize opportunities and mitigate risks for key Scottish businesses and sectors," she said.

After years of tortuous negotiations and a series of political crises since the UK voted 52 percent to 48 percent to leave the EU in the 2016 referendum, Brexit remains up in the air.