Labour conference delegates have been meeting in Brighton
A move to give grassroots Labour members more control over the party's policy-making has been successful.
Nearly 67% of delegates backed changes to allow every member to vote on who sits on the National Policy Forum.
The move - which could lead to pressure for more left-wing policies - was opposed by the party leadership.
Conference chair Cath Speight had said it was not the time for "piecemeal" changes to party structures and efforts should be focused on the election.
But campaigners had insisted it would not spark a return to the "bad old days of internal strife" and would increase democracy inside the party, arguing the old process gave the party leadership too much control.
Labour's annual conference in Brighton voted on the "one member one vote" move on Wednesday and the results were announced on Thursday morning.
At the moment 55 members - more than a quarter of the forum which will meet ahead of the next election to decide the party's manifesto - are drawn from constituency Labour parties.
They have been chosen at the annual conference by the conference floor so the party hierarchy has some control over who gets appointed. It also meant the 20% of party branches which do not send delegates to conference do not get a say.
Eleven constituency Labour parties called for a postal ballot with every member taking part and the unions had said they would not use their block votes against it.
Such a change could lead to more left-wing members of the party being elected to the forum.
The party's ruling National Executive Committee urged delegates on Wednesday to reject the changes, arguing it was not opposed in principle but would examine them as part of a wider review of internal democracy next year.
But Islington North delegate Cat Smith told the conference that the old system was leaving a lot of ordinary members disenfranchised.
Ann Black, a member of Labour's National Executive Committee, told a Campaign for Labour Party Democracy news sheet: "The change would not take the party back to the bad old days of internal strife, as some have suggested.
"That has not happened on the NEC, where I and my colleagues are elected by one-member-one vote, nor in Scotland, where their successful policy forum is already elected through an all-member ballot."