LIBERAL frontbencher Joe Hockey says heterosexual couples don't make better parents than gay couples but he maintains his opposition to gay marriage.

During a television panel appearance alongside Finance Minister Penny Wong, Mr Hockey was asked whether he thought he and his wife Melissa were better parents than Senator Wong and her partner Sophie.

"I don't believe we necessarily make better parents because we're male and female," he told ABC TV.

But Mr Hockey said he remains opposed to gay marriage.

"I think in this life we've got to aspire to give our children the very best circumstances and that is a mother and a father," he said.

Senator Wong admitted Mr Hockey's comments were hurtful.

"It is sad that some families have to feel that they have to justify who they are," she told ABC TV.

"When you say those things Joe, what you are saying not just to me but people like me is the most important thing in our lives, which is the people we love, is less good, less valued.

"I know what my family is worth."

Last week, US President Barack Obama announced a change of heart on the issue and declared his support for gay marriage, however Prime Minister Julia Gillard said her position had not changed.

A parliamentary inquiry is under way into three private members bills that aim to change the Marriage Act.