The Tory leadership contest will enter the next stage later when a second round of voting is held in Parliament.Conservative MPs will vote by secret ballot in the Commons, with a result expected some time after 18:00 BST.
Any of the six remaining candidates will be eliminated from the contest if they come last or fail to secure at least 33 votes.
Those remaining in the race will take part in a live BBC debate in central London on Tuesday evening.
Remaining candidates will face further ballots later this week, where the bottom-ranked MP will be knocked out until only two candidates are left.
The final two names will then be put to a postal vote of the 160,000 Tory party members, beginning on 22 June, with the winner expected to be announced about four weeks later.