Tim Wilson wants Andrew Robb's seat

Human Rights Commissioner Tim Wilson admits stepping down was a tough decision, but he's convinced it's the right one.

Mr Wilson on Sunday announced his resignation from the $400,000 job to run for federal parliament in the Melbourne seat of retiring Trade Minister Andrew Robb.

He'll seek Liberal preselection for Goldstein despite Mr Robb indicating he wanted a woman to take over when he retires at the next federal election.

Those comments sparked speculation Alexander Downer's daughter Georgina Downer could have Mr Robb's backing.

Mr Wilson has served two years of his five-year posting as human rights commissioner, and says it has been the "most invaluable" experience of his life.

However, he believes it's the parliament that can respond to human rights issues and says the people of Goldstein deserve someone who will fight for them.

"This is not a time to be timid. It's a time to be bold," he said in his resignation statement on Monday.

"Our country faces big challenges: debt and deficits, high taxes and youth unemployment, to name a few."

Mr Wilson pledged to continue supporting the work of Aboriginal and Torres Strait Islander Social Justice Commissioner Mick Gooda regardless of what happens with preselection.

Shadow attorney-general Mark Dreyfus said Mr Wilson had done the right thing by resigning from his post.

But he warned against waiting too long to replace him, like the five months it took the government to fill former Sex Discrimination Commissioner Elizabeth Broderick's shoes.

"I think there's a concern if the position is allowed to remain vacant for too long," Mr Dreyfus told ABC radio.