Tory MPs have backed by 127 votes to 50 a change in party rules for electing a replacement for leader Michael Howard.
Mr Howard will stand down before Christmas
The proposals, already agreed by the party's ruling board and senior backbenchers, would give Tory MPs the final say in the coming contest.
Currently MPs select two candidates and ordinary party members vote on them.
The proposed scheme means they will be asked to rate candidates who have the backing of 5% of MPs. The decision then goes back to the Parliamentary party.
Voting in the consultative ballot of Conservative MPs about the leadership began at 1200 BST on Tuesday and ended at 1400 BST on Wednesday.
The result was announced at a meeting of the 1922 committee of Tory backbenchers.
Howard's plan rejected
The plans will now be drawn up into a formal amendment to the Conservative Party constitution.
MPs and local party chairmen will vote on them at a special convention over the summer.
Tory MPs appeared divided over the proposals, with some, including potential leadership candidates Theresa May, Michael Ancram, David Willetts and Andrew Lansley, saying rank and file members should have a greater say, as they currently do.
After Wednesday's vote, Theresa May said: "I am disappointed that we have decided to send out the message that we can't trust our members to make the decision about who should lead our party."
Lib Dem threat?
The current rules were introduced by former Conservative leader William Hague.
The only time they were used, Iain Duncan Smith was elected over ex-chancellor Ken Clarke.
Meanwhile the C-Change think tank has suggested the Tories face a growing threat from the Liberal Democrats.
Its study says that Tory gains at May's general election mask evidence of a continuing fall in the core vote.
Of the 31 seats the party took from Labour at the general election, 18 of these were due to increased votes for the Lib Dems.
Party chairman Francis Maude told BBC Radio 4's Today programme that rebuilding the party and its support base would be a long job.
"Anyone who thinks that this is suddenly going to fall into our lap would be deluding themselves," he said.
Shadow transport secretary Alan Duncan, who pulled out of the leadership race earlier this week, told BBC's Five Live that the Tories needed to widen their appeal.
Other likely candidates for a Tory leadership contest expected in October include Ken Clarke, David Cameron, David Davis, Sir Malcolm Rifkind, Liam Fox and Andrew Lansley.