Johnson's rise comes as Theresa May faces a rebellion from party members who will try to force her out in a special meeting in a few weeks, The Sun reports.

The newspaper quotes a survey of activists by the influential Conservative Home website which shows that 33 percent now back Boris Johnson to become the next Conservative Party leader.

"His resignation catapulted him to the front of the queue as the main Conservative opponent of Theresa May’s EU policy. And the worse she does, the more he thrives", Conservative Home head Paul Goodman said of Boris.

He added, however, that Mr Johnson's success could increase support for the PM among Tory MPs who don't want to see him in Downing Street.

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Boris Johnson is followed by his fellow Brexiteer Dominic Raab at 14 percent, with Michael Gove, Jeremy Hunt, and Sajid Javid following behind.

Several possible contenders, such as David Davis, Matt Hancock, Esther Mc Vey, and Penny Mordaunt are on less than 2 percent each — suggesting they would face an uphill climb, the survey reveals.

The next leader will be chosen by a vote of all Tory members from a shortlist of two selected by the party's MPs.

Prime Minister Theresa May has recently pledged to quit after sealing a Brexit deal. However, now she remains under pressure to step down immediately as the Tories plunge in the polls.

Dozens of constituency chairmen have signed a petition calling for a special meeting of the party where they would hold a no-confidence vote on Mrs May.

Although the motion wouldn't be binding, it would step up pressure on the PM to resign.

Meanwhile, a separate Conservative Home poll conducted on Sunday shows that three-fifths of Tory members are willing to vote for the Brexit Party in the European elections next month if Britain hasn't left the EU by then.