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

Just six months before the UK is due to leave the EU on March 29, 2019, little is clear: PM 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. 

"This is the moment to change the course of the negotiations and do justice to the ambitions and potential of Brexit," Johnson, who resigned in July as foreign secretary over May's Brexit proposals, wrote in Friday's Daily Telegraph. 

Under the headline, "My plan for a better Brexit," Johnson called for a "SuperCanada-type free trade agreement" and cast the EU's backstop proposals for Northern Ireland amounted to the economic annexation of part of the UK. 

The plan outlined by Johnson gained support from other rebels such as Conservative lawmaker Jacob Rees-Mogg who are pushing for a deeper break with the EU. 

"This is an opportunity for the UK to become more dynamic and more successful, and we should not be shy of saying that – and we should recognize that it is exactly this potential our EU partners seek to constrain," Johnson wrote.

In the June 23, 2016 referendum, 17.4 million voters, or 51.9 percent, backed leaving the EU, while 16.1 million voters, or 48.1 percent, backed staying. 

A poll 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. 

But researchers cautioned that a narrow victory for those hoping to reverse Brexit would be heavily contingent on getting those who did not vote last time to turn out. 

May, who voted to stay in the EU, is trying to clinch a divorce deal with the EU while grappling with an open rebellion in her Conservative Party, which convenes in the English city of Birmingham on Sunday for its annual party conference. 

"There has been a collective failure of government, and a collapse of will by the British establishment, to deliver on the mandate of the people," Johnson wrote.

(Cover: Theresa May sits next to Boris Johnson as she holds the first Cabinet meeting following the general election at 10 Downing Street, June 12, 2017. /Reuters Photo)