The attorney general has appointed a director from the rightwing thinktank the Institute of Public Affairs as Australia’s human rights commissioner.

George Brandis said Tim Wilson, a member of the Liberal party until this month, had been appointed to “restore balance” to the Australian Human Rights Commission.

Wilson, a self-declared classic libertarian, directed climate change policy at the IPA as well as the Intellectual Property and Free Trade Unit.

Wilson said he had stepped down from his position at the IPA as well as resigned from the Liberal party to take up the appointment.

He said he was looking forward to “advancing the government’s freedom agenda”.

“As Australia’s human rights commissioner I will seek to reverse the incremental dilution of human rights and reassert their essential status in our community,” he said in a statement on his website in which also thanked his partner, Ryan, for his support.

“I will unapologetically approach this important role with the strong belief that human rights are important, consistent and universal and provide the foundations for a free society.

“As human rights commissioner I will put freedom on the offensive: where it belongs.”

The president of the commission, Gillian Triggs, welcomed Wilson’s appointment, but warned he may have trouble advancing his cause without legislation, such as a bill of rights, to back him up.

The IPA has called for the abolition of the commission and Triggs said it was healthy to have someone bring a fresh view in.

But Triggs said: “There’s no doubt for the most part we do what the legislation allows us to do.

“It will be interesting to see if the attorney general is planning to introduce legislation that will give him a legislative base for the work he wants done.

“There is no charter of rights, no bill of rights, no legal provisions to protect fundamental rights such as freedom of speech, freedom of press and freedom of association.”

She added: “I’m not suggesting for a moment a bill of rights be introduced – we’ve had that debate – but Tim will have a task arguing for freedom without tools of legislation for it.”

Triggs said it would be particularly interesting to see how the right not to be detained without charge enshrined in legislation would work with Australia’s asylum seeker policy.

Wilson said he had not worked out what his specific agenda would be and had not decided if he would be lobbying for rights to be enshrined in legislation.

He said he had accepted the taxpayer-funded position, which pays more than $300,000 a year, because he believed it would be a challenge.

“I’m a classic liberal, I do believe in some taxation and the government has made the decision to keep the Human Rights Commission,” he said.

“If it is going to exist I want to make sure it advances basic human rights.”

When asked if he supported the abolition of the commission, Wilson said he was going to “leave my comments there”.

Brandis released a statement calling Wilson one of Australia’s most prominent public advocates of the rights of individuals.

“He has published and broadcast widely on the topics of personal freedom, liberal democratic values and the rule of law,” he said.

“He was at the forefront in thwarting recent attempts to erode freedom of speech, freedom of the press and artistic freedom.”

Brandis said the appointment restored balance to the commission, which he claimed had become “increasingly narrow and selective” in its view of human rights under the previous Labor government.

Wilson will become the seventh commissioner at the commission, with Triggs having taken on the human rights role since it was left vacant.