LONDON — In a major blow to Prime Minister Boris Johnson, Britain's highest court has ruled that his decision to suspend Parliament for five weeks in the crucial countdown to the country's Brexit deadline was illegal.

The unanimous, strongly worded Supreme Court judgment on Tuesday declared Johnson's order to suspend Parliament "void and of no effect."

The court found that Johnson's suspension had the effect of limiting debate by lawmakers on Britain's impending departure from the European Union in violation of Parliament's constitutional role.

The landmark decision was quickly criticized by Johnson and prompted calls for him to quit from opposition leaders. The Conservative prime minister and Parliament have been at odds since he took power in July with the goal of taking Britain out of the EU on Oct 31 with or without a divorce deal.

Johnson vowed Tuesday that he will not resign and was flying back to London from New York overnight.

Parliament resumes Wednesday.

AP