Julia Gillard, who is strongly opposed to equal marriage, has confirmed she will resign as Australia’s prime minister in favour of Kevin Rudd – with LGBT campaigners welcoming the news.

It follows a leadership ballot of Labor MPs.

Former prime minister Kevin Rudd is now the new Labor leader and is set to be sworn in as Australia’s new prime minister.

Mr Rudd announced his support for equal marriage in May, having previously been against it.

The 55-year-old said he had come to “believe the secular Australian state should be able to recognise same-sex marriage”.

Australian Marriage Equality national director, Rodney Croome, said: “Having a prime minister who supports marriage equality opens up a new chapter in the debate by mainstreaming and legitimising the reform like never before.

“Kevin Rudd’s support for marriage equality will be an important point of difference with Tony Abbott, increasing pressure on Mr Abbott to allow a conscience vote and bringing marriage equality to the centre of the federal election campaign.

“Mr Rudd’s stance will also draw young voters to the Labor Party and galvanise the Labor grassroots behind him, given that both groups strongly support this reform.

“The majority of Australian Christians will also welcome a Christian prime minister who represents their support for marriage equality.”

Julia Gillard remains opposed to equal marriage.

On becoming prime minister in 2010 she said: “We believe the Marriage Act is appropriate in its current form, that is recognising that marriage is between a man and a woman, but we have as a government taken steps to equalise treatment for gay couples.”

She ruled out introducing equal marriage in May following neighbouring New Zealand’s decision to introduce the measure.

Along with Julia Gillard, Australia’s opposition leader Tony Abbott continues to oppose equal marriage and refuses to allow his Liberal MPs a conscience vote.