Tramways Union is calling for action after a bus driver was seriously assaulted last night in Auckland's Waterview

The sustained assault on a bus left the driver in hospital in a serious but stable condition.

It's the second time he's been assaulted at work in the past month.

Union President Gary Froggatt says drivers need more tools to deal with unruly passengers.

He says staff should be given more training in how to deal with these types of incidents.