A former national secretary of the Australian Labor Party, Bob Hogg, has called for Opposition Leader Bill Shorten to resign, accusing him of failing to understand the concept of conflict of interest.

Mr Hogg attacked Mr Shorten after the Labor leader on Wednesday admitted he had failed for eight years to reveal that a labour hire company had paid the salary of his campaign director in the 2007 election campaign.

The company had been involved at the time in negotiations with the Australian Workers Union for a new enterprise bargaining agreement for its workers, the royal commission into trade unions was told.