Qantas boss Alan Joyce has hit back at criticism from Government minister Peter Dutton, saying that while same-sex marriage does make economic sense for his company, ultimately that is not the reason for the national carrier's support.

Instead, he said Qantas just did not believe "some people should have fewer rights than others".

Mr Dutton last week scolded Mr Joyce for using the Qantas brand to campaign on the issue.

"Mr Joyce is an exceptional CEO. He's a good person and I know him personally — I have no gripe against him," the Immigration Minister said then.

"But if he has a particular view on any issue it should be expressed as an individual.

"It is unacceptable that people would use companies and the money of publicly listed companies to throw their weight around."

Mr Dutton's comments followed the release of a letter organised by the Australian Marriage Equality organisation — and signed by 20 chief executives, including Mr Joyce — which called on the Prime Minister to legislate same-sex marriage.

Qantas defended its decision in a public statement and vowed to continue supporting same-sex marriage.

Writing on the Qantas website on Tuesday, Mr Joyce said companies did have a role in the community "beyond selling it things".

"In the past few years alone, Qantas has given its support widely. Charity flights for drought relief. Awareness raising for homelessness. Transporting volunteer firefighters around the country," he said.

He listed Qantas's support for same-sex marriage alongside its recognition for Indigenous people and campaigns for gender equality.

Mr Joyce also wrote that it was an economic issue, saying, "more open societies attract better talent".

"Qantas (and its CEO) is often called on to speak publicly on issues like company tax, industrial relations and trade. And we do. Because these are important issues that ultimately shape what kind of society we live in (which is the point of economics, right?)," he wrote.

"We're pleased to include marriage equality on the list."

Foreign Minister Julie Bishop seemingly disagreed with her colleague's criticisms at the time, and said Australia was a democracy where free speech should be protected.

"People are free to take part in public debates, and this is an issue that I'm sure will be the subject of public debate for some time," she said.

"And so, if chief executives believe that it's in the interests of their company to collaborate on a public statement, then they're free to do so."