Senator Michaelia Cash will give evidence during a court hearing over federal police raids on two Australian Workers' Union offices, but timing is an issue given the trial coincides with federal Parliament's only sitting week before the election.

The AWU is taking Federal Court action against the Registered Organisations Commission, challenging the lawfulness of raids by Australian Federal Police on union headquarters in Melbourne and Sydney in October 2017.

The raids drew media scrutiny when journalists arrived before police after a tip-off from the office of Senator Cash, the then jobs minister.

AAP