The UK's next prime minister will be announced by next Friday, Sir Graham Brady, head of the Conservative backbench 1922 committee has said.
Candidates to replace Liz Truss will need at least 100 nominations from Conservative MPs. Nominations can be made from now onwards and will close at 2pm on Monday.
Nominations can be accepted either by email or signature.
An online vote will then be held for Tory members if two candidates make it through the parliamentary stages by the Monday deadline.
Sir Graham added that "all outreach efforts will be made" for members without internet access.
Results from an "indicative vote" among MPs after two candidates remain will be released for Tory members, in order to get an indication of the mood among Tory MPs. This change to the procedure was not included in the previous contest.
Chair of the 1922 Committee Sir Graham Brady and Tory party chairman Jake Berry announce the process for the upcoming Tory leadership contest.
One television event will be held after Monday so party members and the wider public can hear from the leadership candidates.
It is hoped the entire process will be concluded by next Friday, with Sir Graham saying he expects the new leader to be in place by then.
The leadership contest follows Liz Truss's resignation as Prime Minister on Wednesday, after just 44 days in office. Her announcement makes her Britain's shortest-reigning prime minister.
Tory party chairman Jake Berry said the board of the Conservative Party met at 4pm and, in conjunction with the 1922 Committee, had decided on the process.
The bar for nominations has risen since the previous leadership contest, where only 20 nominations were needed from Conservative MPs.
Robert Peston sums up an extraordinary 45 days in 45 seconds
While Brady said the threshold is "high", he told ITV News Deputy Political Editor Anushka Asthana that it "should be achievable by any serious candidate who has any realistic prospect of going through".
According to ITV News Political Editor Robert Peston, very few Tory MPs are likely to get 100 initial backers.
Mr Peston added: "[Mr Berry and Sir Graham] both said there is the facility for there to be a vote by members, but they couldn’t rule out that MPs would stitch up an agreement between themselves, that they’d only be one left.
"So I think it's possible that by Monday or Tuesday, we could know the identity of Britain’s new Prime Minister."
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Former chancellor Rishi Sunak, who was runner-up to Ms Truss in the leadership election and topped the voting among MPs, could be a popular option for Tory members, with Conservative MPs reportedly exploring a joint ticket with his fellow contender Penny Mordaunt. Boris Johnson is also expected to attempt an extraordinary political comeback in the race to replace Liz Truss, a little over six weeks after the scandal-battered MP was forced out.
There is deep concern from some MPs and security analysts that the election's rapid electronic voting brings risk of hackers skewing the poll.
Mr Berry said he was confident the voting system will be secure.