Harriet Harman
The interim Labour leader said hustings should be televised and held in marginal constituencies (Getty)

Labour will ensure that their union backers do not have an undue influence over the party's leadership contest by making sure everyone's vote is equal.

Harriet Harman, the interim Labour leader, explained that the independent Electoral Reform Society will send out ballot papers to every party member ahead of the vote.

Harman said that people could sign up to the party for just £3 ($4.7) and have a vote in the election. The Labour grandee also argued that the hustings should be televised and held in marginal seats.

"This is the first time a political party in this country has opened up its leadership contest in this way and I think there will be a real appetite for it out there," she said.

"We have changed the rules so that it means one person has one vote regardless whether they are an MP, a Shadow Cabinet member, a trade unionist or a registered supporter – everyone's vote is equal, as it should be."

Andy Burnham, Yvette Cooper, Liz Kendall and Mary Creagh have all launched their leadership bids after Ed Miliband stood down in the wake of a dismal general election performance for Labour. Tristram Hunt, the shadow education secretary, is considering putting his name in the hat.

The race hosted some early drama when Chuka Umunna pulled out of the contest just days after launching his campaign. The shadow business secretary reportedly cited press intrusion as the main reason behind his move.

Meanwhile, a debate over Labour's relationship with its trade union affiliates erupted over the weekend after Jim Murphy slammed Unite's Len McCluskey as "destructive" when he resigned as Scottish Labour leader.

The remark came after the union boss opposed Murphy's election last year when he backed Labour MSP Neil Findlay.

McCluskey said he thought Murphy was "hurting" when he made the scathing attack but the Unite man accused Murphy of "arrogance".

"He represented the ideology that has completely alienated [voters], not just in the election, not just in the [2014 independence] referendum, but for years," McCluskey told the BBC.

"Since 2008 the SNP have been gaining ground and Scottish Labour have displayed an arrogance that unfortunately led us to where we were at the general election."

The labour movement in-fighting broke out after Unite donated millions of pounds to Labour in the run-up to the general election in a failed bid to keep the Tories out of office.