The latest attacks left a Maori Warden with bruises and put a ticket inspector off work with undisclosed injuries after he was hit from behind at Papakura by an unseen assailant.
Although the company is vague about the number of violent incidents on the trains it runs under contract to Auckland Transport, the Rail and Maritime Transport Union says it knows of 12 since January.
General secretary Wayne Butson welcomes the extension of hours for Maori Wardens, but says that follows despair among his members over slow responses to calls for action.
Mr Butson said most assaults were committed by fare evaders, a situation he claimed was created by Auckland Transport no longer allowing ticket sales on trains. The problem was exacerbated by a failure of lawmakers to prescribe penalties against fare evasion.
A spokesman for the council body would not comment on the latest assaults.
But chief operations officer Greg Edmonds said AT was "continually working with Transdev on ways to reduce violence against their staff - it won't be tolerated".
Train violence
*12 assaults on Auckland rail staff since January alleged by union, including two this month on the southern line.
*Windows smashed on eight passenger trains by rock-throwing vandals in February on the western line.