St John staff who are members of the First Union started a three month partial strike from Christmas Day, after collective agreement negotiations continued to break down.
The union's spokesperson Jared Abbott said he received confirmation of the withdrawal from the Employment Relations Authority today.
He said the decision confirmed what the union had suspected - that St John had no intention of reaching an agreement.
Mr Abbott said St John had spent less than two hours at the bargaining table and the service had never proposed terms for a collective agreement.
St John has said it will consider the union's comments and respond on Monday.
Yesterday St John confirmed that striking ambulance staff who refused to wear a high-visibility vest while out on jobs would have ten percent of their pay cut.