A union is threatening to "shut down the banking system" after failed negotiations with cash-in-transit company Armourguard Currency Management.
About 40 Armourguard Currency Management (ACM) workers, who are charged with filling up ATM machines, are striking today in Auckland and Wellington.
The industrial action has left ATM machines empty after the long Easter weekend, the Service and Food Workers Union (SFWU) claims.
SFWU workers advocate Jill Ovens accused ACM of being "absolutely unprepared" for negotiations on a new collective agreement for workers in January.
Union members wanted to send a clear message to their employer that ACM should take the negotiations seriously, she said.
"Our members have the power to shut down the banking system."
Wellington delegate Greg Kane said the mediation was a "big let-down".
"We outlined yet again our position on the outstanding clauses and then they asked us when we would be able to meet again. It was all over by lunchtime."
Jill Ovens said ACM had not moved its position on workers' pay rates, overtime or redundancy.
The company had hardened its position on other issues, including how many hours make up a full time job, she said.
"Some of our members have individual agreements guaranteeing as few as 30 hours a week."
Other difficult issues included the introduction of random drug and alcohol testing, Ms Ovens said.