The timetable and rules of the contest to replace Boris Johnson as leader of the Conservative Party and prime minister were announced on Monday evening.
Sir Graham Brady, chair of the 1922 Committee of backbench Tory MPs, said nominations would open and close on Tuesday.
A first ballot of Conservative MPs will be held on Wednesday with a second vote taking place on Thursday, he said.
Crucially, he also announced that each candidate would need at least 20 nominations from fellow Tory MPs to make it onto the first ballot - a higher number than in previous contests.
It comes after one of the contenders to replace Mr Johnson, Sajid Javid warned the Conservatives face “electoral oblivion” if they do not change.
Launching his bid to be prime minister on Monday, the former health secretary said: “Over the last couple of years, our reputation on most values and policies has slid away. Too many people now believe that Labour are fit to govern. Some of them say that Labour are more competent and even more likely to cut taxes.”
So far 11 Tory MPs have put themselves forward for the top job following Boris Johnson’s resignation last week - with Home Secretary Priti Patel set to decide whether she’ll join the race. Earlier, Liz Truss joined the bidding war, vowing to cut taxes “from day one” and scrapping the NI hike that hit in April.
