Two of Britain's leading constitutional experts have said would-be Conservative Party leader Boris Johnson might not become the country's next prime minister even if he wins the vote to replace Theresa May as party leader.

Johnson and Foreign Secretary Jeremy Hunt are currently trying to win over the support of party members nationwide before a vote takes place at the end of July to decide who should succeed May and despite a problematic campaign, Johnson remains the favorite.

However, several leading Conservative members of Parliament have said they would not be willing to support any possible Johnson administration because of his comments about the possibility of a no-deal Brexit, which could potentially create the circumstances of someone who should be taking over a prime minister knowing from the outset that they do not command a majority in Parliament.

"Whether the new Conservative party leader can command parliamentary confidence is clearly in some doubt given comments from Conservative MPs that they may not be able to support the new government," wrote Robert Hazell and Meg Russell from the University College London Constitution Unit.

"One possible scenario is that a group of Conservative MPs is so concerned about the winning candidate that they declare their withdrawal of support immediately the result of the leadership contest is known-for example, before the new PM is appointed. This would pose a serious dilemma for the queen and those advising her, because it would not be clear that the new Conservative leader could command confidence."

In the three years since the popular vote for the country to leave the European Union in June 2016, the Brexit crisis has claimed the political lives of two prime ministers-David Cameron and Theresa May-and could now scupper a third before it has even begun.

With her Brexit proposals having been rejected by Parliament three times and the party more deeply divided than ever over the issue, on May 24 the current prime minister announced that she would step down as Conservative leader, and also national leader.

May remains in Downing Street until her successor is chosen, and part of her role as incumbent prime minister is to recommend to the queen who should form the next government. But Johnson's comments about Britain's departure from the EU have only made the situation more complicated.

The twice-delayed departure date is currently set for Oct 31, a date which Johnson described as "Do or die. Come what may," only to subsequently backtrack, saying he thought the prospect of a no-deal Brexit was a "million to one chance".

Were a Johnson premiership to be ruled out, the alternative is unclear, as the opposition Labour Party does not have a sufficient number of seats to form a government in its own right.

What looks more likely is that, should he win, Johnson would become prime minister at the end of July, but face a vote of no confidence almost as soon as Parliament returns from its summer recess. This could be followed by a general election-either called by Johnson to assert his authority, or forced upon him by rebel MPs.