Keir Starmer has abandoned one of the most controversial aspects of his plans to change how the party selects its leaders, but will seek to bring in changes to significantly toughen selection of leadership candidates.

Starmer ditched plans to return to the electoral college after resistance from Labour party members and trade unions.

After late night talks with union bosses, the Guardian understands Starmer will agree to retain the one-member one-vote system but has proposed dramatically increasing the threshold for future leadership candidates to get on the ballot.

Candidates would need 25% of MPs to nominate them to reach the ballot that goes to members. The party will also abolish registered supporters and put a freeze date on membership prior to the start of any contest.

“The aim of the reforms was to ensure that leadership elections are not decided by people who have only joined with the express intention of backing a candidate and have no other relationship with the party,” one Labour source said.

The move, which is yet to be agreed by all trade unions, will be put to the ruling national executive committee on Saturday morning.

The Guardian understands Starmer has also agreed to look at how more trade union members can be given the vote in leadership elections, including those who pay the union’s political levy, which could give another 2.2 million people the right to vote in leadership elections.

Originally Starmer proposed a return to the electoral college, which would give one-third of the vote to unions and a third to Labour MPs, with members making up the rest. On Friday morning, a senior Labour source said the electoral college plan was “dead”.

Allies of the deputy leader, Angela Rayner, have been furious that key announcements on workers’ rights during her media appearance on Saturday morning have been drowned out by relentless media questions on internal warfare.

Starmer will also press a change in the way the party selects its MPs, which has been promoted as a way to free MPs from having to fight lengthy re-selection processes before elections and allow them to focus on the voters.

Starmer pulled plans to put the proposals to a vote on Friday night to give time for more talks.

Trade union sources said Starmer had made an emollient speech to Tulo, the group that represents the Labour-supporting unions – but that none of the unions present had backed the original plans.

One source suggested Starmer had received a “mauling” for announcing the plans to drop the one-member-one-vote system to elect the party leader without consulting unions in advance.

A spokesperson for Starmer said: “The Labour leader will be putting a package of party reforms to the NEC that better connect us with working people and re-orient us toward the voters who can take us to power.”

Another source said: “Keir said on Tuesday it wasn’t a take-it-or-leave-it deal. That’s how we’ve approached it and we’re pleased with where we’ve ended up.”

Rayner, the shadow secretary of state for the future of work as well as Starmer’s number two, has privately made clear that she would like the conference to focus instead on attacking the government and setting out Labour’s offer to the country.

Others who had publicly expressed reticence at the proposed reforms included the London mayor, Sadiq Khan, the mayor of Greater Manchester, Andy Burnham, and the Scottish Labour leader, Anas Sarwar.

Rayner will set out plans at the party’s annual conference later on Saturday for fair pay agreements aimed at strengthening workers’ bargaining powers, particularly in sectors plagued by low pay and insecure contracts.

The policy, which echoes an approach recently adopted in New Zealand, would introduce government-backed negotiations between unions and employers across an entire sector, rather than firm by firm. These would set minimum pay rates and basic conditions, which would then become a mandatory “floor” across the sector.