Julia Gillard has admitted she was “wrong” to oppose same-sex marriage while she was prime minister.

Ms Gillard later changed her mind, publicly supporting the 2017 campaign for same-sex marriage when then-Liberal prime minister Malcolm Turnbull oversaw the national postal survey. It had the backing of more than 60 per cent of respondents and ultimately led to the change becoming law.

Ms Gillard opens up on the issue in an appearance on ABC TV’s The ABC Of… with David Wenham this week.

In the episode, which airs on Tuesday night, Wenham asks Ms Gillard if she was obliged to “play politics” on same-sex marriage during her time in parliament.

“I wouldn’t say obliged but it was a political issue,” she said.

“As a feminist I always wanted us to have a deeper debate about the role of marriage and I thought maybe this was the moment for the deeper debate.

“I got that wrong, you know, got it incredibly wrong and very happy to say that.

“Then, as the campaign for change grew stronger and stronger and it became clear that the only debate to be had was marriage equality, then I was very happy to support marriage equality.”

Ms Gillard was PM from 2010-2013. She voted against a bill for marriage equality in 2012, before telling a Melbourne audience in 2015 – two years after she left politics – that she had changed her view on the issue.

“Given the 1970s feminist in me saw much to be concerned with from a gender perspective with traditional marriage, I thought the better approach was not to change the old but to create something new,” she said.

“In my time post-politics, as key countries have moved to embrace same-sex marriage, I have identified that my preferred reform direction was most assuredly not winning hearts and minds.”

Ms Gillard was the object of astonishing sexism during her term as PM. She has previously spoken about how it worsened as her term went on – from being asked on Perth radio if her then-partner was gay, to to discovering a Liberal National Party fundraiser menu had served a ‘Julia Gillard’ quail (featuring “small breasts, huge thighs and a big red box”).

With Wenham, she also reflects on her now famous misogyny speech, delivered on the floor of parliament in 2012. The speech attracted global attention – something Ms Gillard tells Wenham once made her “a little bit resentful” because it overshadowed her political work, such as the introduction of the National Disability Insurance Scheme.

“For a period, it was all everybody was talking about in terms of my time in office,” she said.

“But I’m well and truly at peace with it now because most leaders don’t get remembered for very much is the truth of it. They certainly don’t get internationally recognised for very much.

“So now, as I spend quite a bit of my life overseas and I have people talk to me about that speech, it’s sort of the only thing they know about Australian politics.”

Ms Gillard said she now realised that when she was first elected to parliament in 1998, women were showing they could cope and survive in parliament.

“We were proving we could be great backbenchers, and then proving we could be great shadow ministers and then proving we could be, you know, cabinet ministers in government and on it went,” she said.

“Until women have answered that ‘can women do it?’ question – which people don’t articulate but they definitely think – until you’ve answered that, you don’t get the freedom to then say, ‘and now, let’s change the environment and make it really different.'”

“I think we’re at that stage now and that’s a great stage to be at.”

She said it would be impossible for another woman MP to now be subjected to the same gendered criticism she was, and the political price of doing so would be “huge”.

• Julia Gillard is on The ABC Of… with David Wenham at 8pm Wednesday