An air conditioning fault at Austrlian bank Westpac’s data centre denied customers access to banking services for a few hours earlier today.

Westpac bank has Australia’s largest branch network and an estimated 12 million customers, who were effected by the nationwide loss of ATM service, Point-of-Service transactions and online banking today. In a statement, the bank said the fault was due to "an outage caused earlier today by an air-conditioning fault at a data centre".

All services were restored before the end of the morning, Australian time. The crash came 24 hours after Westpac announced a record profit of AU$4 billion.

Westpac outsources its IT infrastructure including data centres to IBM. Last November, the bank signed a five year extension to this outsourcing deal, which IBM said at the time was "built around improving service quality for bank staff and customers, lowering risk, increasing cost control and supporting Westpac’s business agility".

In December last year, National Australia Bank outsourced 425 IT roles to IBM just weeks after a corrupt file caused its system to crash.