Australia’s Coalition leader and head of the Opposition has lauded his sister for bravery in coming out, but remains staunchly opposed to gay marriage.

Tony Abbott said it was brave of his 47-year-old sister Christine Forster to confirm her relationship with Virginia Edwards. However, this would not affect Coalition’s marriage policy.

‘We've had a lot of interesting discussions and we'll keep those discussions going, but fundamentally I want to be a politician that keeps my commitments,’ Abbott told The Sunday Telegraph.

‘We went into the election with a position and as far as I'm concerned, that's the position we will keep.’

Previously married with four children, Forster drew media speculation and then publicly came out after being photographed to support gay marriage at a concert with Edwards last year.

Abbott is reported to have known his sister’s sexuality four years ago. She came out to the public after extensive consultations with the family.

While ‘spirited’ discussions at family gatherings did not change Abbott’s mindset, he said he admired the way his sister had handled the situation.

‘She has had some very difficult and complex issues to deal with and I really admire the way she's handled it,’ he said. ‘I think she's handled it with courage and authenticity.’

Gay marriage advocates praise Abbott’s showing of respect and love to his sister and remains hopeful his stance would soften.

Of influential Opposition players, New South Wales leader John Robertson and communications spokesman Malcolm Turnbull, among others, have called for a conscience vote on gay marriage.

‘I think family circumstances are a personal issue,’ said Robertson, who has a gay son and supports same-sex marriage.

A poll late last year showed that 76% of supporters of the Coalition backed a free vote.