Known for his unconventional political style, the 52-year- old journalist-turned-Conservative politician had led the Brexit camp in the June 23 referendum, falling out with his mentor and party leader Cameron who aggressively campaigned for Britain to stay in the 28-member EU.
Other candidates emerging in the fray include UK's longest-serving home secretaries in history, Theresa May, who turns 60 later this year and has reportedly gathered strong support, followed by UK health secretary Jeremy Hunt.
May was backed by 19 per cent of the public, compared to 18 per cent who backed Johnson.
A number of other Conservative MPs were also scrambling to build up support for themselves as potential candidates to replace Cameron, who was elected party's leader in 2005.
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The 54-year-old former defence secretary, Liam Fox, who finished a close third during the 2005 contest for Tory party leadership, is also expected to throw his hat in the ring for a second time.
However, UK Chancellor George Osborne has ruled out his candidature.
"I was full-throttled in arguing for remaining in the EU and because half my party wanted to leave the EU I don't think I can be the person to bring this party together, at the moment," he told BBC today.
He said the right candidate to lead the party and the country was the person who is "able to articulate the clearest, crispest version of what relationship we are seeking" with the EU.
The Conservative party's Committee had yesterday announced a leadership timetable, which will see two short- listed candidates go head to head to be elected new leader by September 2.
"That ought to mean that we would have a new prime minister before the House of Commons returns for its September sitting."
Nominations for the race to succeed Cameron open tomorrow and close on Thursday, with backbenchers meeting to approve thecompletetimetable for the contest.
Whoever next ends up in No. 10 Downing Street will begin extracting the UK from the economic bloc as Cameron said it will be the new Prime Minister who will take the negotiations forward.