Brexit campaigner Boris Johnson called on Prime Minister Theresa May to rip up her proposal for Britain's exit from the European Union, ratcheting up the pressure on May as she prepares to face her divided party at its annual conference next week.

Just six months before Britain is due to leave the European Union on March 29, 2019, little is clear: May has yet to clinch a Brexit divorce deal with the EU and rebels in her party have threatened to vote down any deal she makes.

Adding to the uncertainty, a poll of polls published on Friday showed voters would now vote 52 to 48 percent in favor of remaining in the EU were there to be another Brexit referendum. May has repeatedly ruled out another referendum.