Commissioner under fire over US trip

Human rights commissioner Tim Wilson is under fire for attending a friend's wedding in San Francisco last year while he was in the US on official business.

Mr Wilson, appearing before a Senate estimates in Canberra on Tuesday, insisted he covered the costs of his private business accommodation and flights.

Government senator Barry O'Sullivan expressed frustration at Labor's line of questioning saying the hearing had spent an hour on the "Holiday Inn incident" when there were more important issues to discuss.

The hearing was also told Mr Wilson had resigned his Liberal Party membership at the request of Attorney-General George Brandis.

Labor senator Jacinta Collins said the Human Rights Commission was becoming a "holding pen" for Liberal Party candidates.

She noted Mr Wilson had been slated for various Liberal Party preselections.

As well, there was speculation Peta Credlin, the chief of staff to former prime minister Tony Abbott, might become the sex discrimination commissioner.

Two commissioners - Susan Ryan (age and disability) and Tim Soutphommasane (race discrimination) - previously had links to the Labor Party.