Ms Harman has launched a new Equalities Bill
One of Labour's top two posts should always be held by a woman, Deputy Leader Harriet Harman has told a paper.
She does "not agree with all-male leaderships" because men "cannot be left to run things on their own" she told the Sunday Times.
A balanced team of men and women make "better decisions," she added.
The MP reportedly tried to change the party's rules to ensure a female was always in a top job shortly after winning the deputy leadership contest.
In an interview with the paper, Ms Harman said she thought there would never be a men-only team of leadership in the Labour Party again.
"People would look at it and say, 'What? Are there no women in the party to be part of the leadership? Do men want to do it all themselves?'," she told the paper.
She said the party "owed it to women" to have a female in one of the two top jobs, to makes sure the concerns of women voters were properly taken into account when decisions were being made.
Female political leaders were "coming of age" internationally, she added.
Speaking on the BBC's Andrew Marr Show, Ms Harman said the government had a "team of women and men ministers making sure this country gets through this economic crisis".
She said comments Labour had already lost the next election were "insufferably arrogant" and "a team of women and men in Labour - which is the party of equality - were fighting to win".
Her remarks follow Lord Mandelson's call for Labour to "roll its sleeves up" and take the fight to the Conservatives.
Former Conservative minister Ann Widdecombe dismissed the idea of reserving one of Labour's top posts for a woman as "remarkably silly" and said jobs should be handed out on merit.
"As long as women are in Parliament, and are good, then I don't have a view on whether the entire Cabinet is male or female," she said.
Special processes to encourage females to get to the top were "demeaning," particularly if the processes "involved positive discrimination" or "unjustified over-promotion," she added.
Ms Harman has led a campaign to promote more women to top jobs, particularly in the City.
Under her controversial new equality bill, women will find it easier to demand equal pay and employers will be given a legal right to discriminate in favour of female candidates.