"We have requested urgent talks with Auckland Transport and Transdev today to try and resolve this issue through discussion, however our members are resolute: they do not want to inconvenience passengers but they will not compromise public safety,'' he said.
Kerr said if the plan went ahead the railway would become a "criminal's paradise".
"Uniformed staff deter criminal and anti-social behaviour and it's vital they are on every train. Furthermore, getting rid of on-board staff endangers the travelling public as these people are first responders in the event of medical emergencies and on-board and trackside incidents."
Meanwhile, Wellington's rail workers are striking again tomorrow - the second time in two weeks.
Workers will strike from 2am until midnight over dissatisfaction with how they are treated by their employers - Transdev and Hyundai Rotem.
"Despite going into mediated bargaining, there's been no meaningful change from Transdev and Hyundai," Wayne Butson, rail and marine transport union advocate, told the Herald.
The first strike, for two hours on November 16, was the first to hit the Wellington rail system for 20 years.