Users of Westpac's online banking services will face disruption later this week when IBM technical support staff begin strike action, warns the Australian Services Union.
The industrial action follows a unanimous vote in favour of industrial action following IBM's refusal to negotiate a collective agreement.
The 45 technical support staff, based at IBM's "flightdeck" centre in Sydney, maintain computer systems and critical infrastructure for the bank, says the ASU.
The employees, who also maintain systems for airlines Qantas and Cathy Pacific and the Australian Customs Service, plan four hour rolling stoppages from Wednesday.
The union is warning that the strike could lead to "total chaos" and leave services in "meltdown".
Sally McManus, branch secretary, ASU, says: "Airport customers will face flight delays, billions of dollars may not be processed for Westpac and Customs won't be able to keep track of security checks, all because IBM refuses to talk to its employees."
But despite the union's claims, IBM told local press the it expects the strike to have little impact on its customers operations.