Australia’s general election will be held tomorrow and marriage equality has become an unexpected hot issue.

Some parts of the country allow civil unions but marriage for gay couples is not permitted.

Both prime minister Julia Gillard and her opponent Tony Abbott, of the centre-right Liberal Party, have been challenged on their positions in the last week.

Neither support allowing same-sex couples to marry.

Ms Gillard, an unmarried atheist, told the Australian this week that she respected the country’s Christian heritage and added: “The Marriage Act has a special status in our culture.”

Mr Abbott, who is Catholic, told a questioner at a debate that he did not support same-sex marriage but hoped he would “always find it in my heart to treat people the way everyone should be treated – with dignity and respect”.

The Liberal leader told a radio programme in March that he felt a “bit threatened” by homosexuality. He later apologised for his choice of words and said he would support recognising committed gay relationships.

Gay marriage supporters say polls show that the majority of Australians support allowing gay couples to marry.

The secretary of Australian Marriage Equality, Peter Furness, attacked Ms Gillard for her remarks on the country’s Christian heritage.

He said that Spain, Portugal, Argentina, Mexico all allow gay marriage and have a much longer Christian heritage than Australia.

He added: “We demand to know how far Gillard will go in the name of our ‘Christian heritage’ – will she outlaw divorce and interracial marriages, recriminalise homosexuality and abortion, suppress atheism, and remove herself and all other women from leadership roles?”

Labor politician Penny Wong, who is a lesbian, provoked anger and accusations of “selling out” gay people last month when she said that religious and historical views of marriage should be respected.

Last week, Wendy Francis, a Family First candidate, apologised for offending people after claiming that gay marriage was “emotional child abuse”.

Ms Francis, who also claimed that children brought up by gay couples would suffer “uncontrollable depression and suicide”, apologised for causing hurt but said she stood by her views.