Ms Truss resigned on Thursday just six weeks into the job, making her tumultuous premiership the shortest in British history.Candidates to replace her need support from at least 100 colleagues, limiting the contest to three.
Former PM Boris Johnson has not ruled out a dramatic comeback, months after being forced out after a Tory revolt.
Rishi Sunak and Penny Mordaunt, who stood unsuccessfully in the contest to replace him, are also seen as likely contenders to run again.
