Western Health spokesman Andrew Williamson said it was too early to tell if services would be affected by the ongoing action, but at this stage operations were running smoothly.

Paramedics want longer rest breaks to combat what they say is on-the-job fatigue.

Ambulance Employees Australia state secretary Steve McGhie said paramedics felt betrayed by the Government's failure to support 10-hour rest breaks.

"Paramedics are taking this action because every day they are forced to make life-and-death decisions in a fatigued state.

"It's time for Premier [John] Brumby to decide if he wants fatigued paramedics responding to critically ill patients."

Ambulance Victoria general manager of operations Tony Walker said the union bans were being closely monitored.

"The bans, at the moment, are not having a dramatic effect on our workload," Mr Walker said.

"Predominantly, this is because our paramedics have only one day in eight when their minimum rostered break is 10 hours, and every other day it is a minimum of 14 [hours].

"As such, the only time our paramedics don't have a 10-hour break is when they are treating a patient at knock-off time and have to work incidental overtime."

Year-long negotiations broke down. After a two-week hearing before the Industrial Relations Commission that concluded last week, the issues remained unresolved.

Last weekend, paramedics began an escalating campaign of industrial action that could result in the first ambulance staff strike in 36 years.

Mr Walker said Ambulance Victoria was keen to resolve the union's pay claim. The union had been offered a number of alternative rosters to accommodate its demands for a 10-hour break.

"However, they have refused these offers and have not provided any options of their own," he said.

"They also do not wish to progress their pay rise argument that would result in an average 16per cent pay increase for paramedics in the first year."

Since Friday, paramedics have defied the eight-hour rest break between shifts policy and are taking 10-hour breaks.