At a private dinner with three same-sex couples on Tuesday Australian prime minister Julia Gillard said gay marriage in Australia was 'inevitable' but she has not announced a change of heart from her opposition.

Before the three-course meal at Gillard's official residence in Canberra Matthew Miller, 12 explained why he would like his mothers to be able to marry. ‘Since they’re not allowed to get married, they’re basically being called not normal and we’re not known as a proper family,’ he said. ‘I don’t know really why I am here, to me, it is simple and this argument should have been settled long ago. People should be allowed to marry the person they love and to be accepted by all society.’

Matthew Miller’s mothers Sandy Miller and Louise Bucke attended the dinner with Sharon Dane and Elaine Crump, who married in Canada but their status is not recognised in Australia, and Steve Russel and John Dini.

Dane, an academic in Brisbane, told ABC Radio that Gillard was respectful of their views but didn’t change her mind. The dinner was won at a charity auction for $31,000 (Australian dollars, $32,944, €24,864) by campaign group Get Up!

‘People are going to say, “Did you say the magic thing to change her mind?” and that's obviously not going to be the case,’ Dane said. ‘She is still standing by her position but she made it clear that she thinks change is inevitable and there will be international pressure that will make change inevitable as well.’

Alex Greenwich, national convener for Australian Marriage Equality was also at the dinner. ‘We all got the impression that her [Ms Gillard’s] opposition was not immovable,’ he said afterwards.

Greenwich urged supporters for marriage equality to submit to the current senate inquiry into the issue. ‘Make sure your submission includes your personal story, the facts and figures about marriage equality, and is respectful and constructive,’ he said in a mailout to supporters.

Gillard, who lives with her partner Tim Mathieson but is not married, is currently fighting a leadership battle for the Australian Labor Party and the country with long-time rival Kevin Rudd.