Fine Gael's grassroots membership will have a say in the party's next leadership contest, following a special party delegate conference at the weekend.
Under the changes, TDs, senators and MEPs will control 65 per cent of the electoral college votes; 10 per cent will be held by councillors and 25 per cent by ordinary members.
Once a vacancy arises, a 21-day election campaign will be held that will include regional debates where candidates will face questions from party members.
The majority of the votes will remain under the control of the Parliamentary Party, since the party's executive council accepted that a party leader could not operate without their support.
Proposing the motion, executive council member Mr Brendan Heneghan said it was similar to one put forward by the party's 1993 "Committee on Renewal".
Carlow/Kilkenny TD Mr Phil Hogan said the new leadership rules "will not be needed for a very considerable period of time.
"I expect that Enda Kenny will be into his third term as Taoiseach before that will happen. We are a very united party.
"I am glad to be able to say that because it wasn't always that way," said Mr Hogan, who was in charge of the party's local and European election campaign.
However, former Fine Gael leader Mr Alan Dukes, who was a member of the committee that proposed the change, voiced strong opposition.
Though he said he did not want "to enter a note of discord", Mr Dukes said he believed the proposal would be "unwise, impractical and not suitable for a properly organised political party.
"We have a representative parliamentary democracy. We elect people to do certain things on our behalf, i.e. members of the Oireachtas.
"That is where the real decisions are made. We trust them to do certain things," said Mr Dukes, urging delegates to vote against the motion.
He warned that the rules would force the party to hold a leadership election after a general election, but before the first meeting of a new Dáil.
However, a delegate, Mr Brian Murphy, said the party's rules made it clear that a leadership election should take place "within two months" if FG was not going into office.
Urging backing for the motion, Mr Jerry Buttimer said Mr Dukes would not have lost the leadership in 1990 because of his support base amongst the party's grassroots.
Wexford delegate Mr Peter Cosgrave said the British Conservatives had brought a similar change in during the early 1990s and lost every election since.
However, the motion passed easily, by approximately 85 to 15 per cent, when it was put to a vote by the executive council chairman, Mr John Delamere from Longford/Westmeath.
Meanwhile, the Athlone conference rejected an attempt to curb the "one man, one vote" system that has chosen the party's election candidates in recent years. If passed, the executive council motion would have restricted votes to members who are properly registered for two years. One executive council member, Ms Leonora Carey, said such a restriction would ensure "that abuses will not continue".
Cork county councillor Mr Kevin Murphy said the existing system "is an absolute fiasco" and had caused him some of "the most turbulent times in my life".
Opposing the restrictions, Fine Gael TD and MEP Mr Gay Mitchell said candidates who attracted in new branch members should be rewarded, not penalised.
