Telstra's mobile networks across the country stopped functioning for several hours on Tuesday afternoon after a key piece of equipment was accidentally switched off, causing major problems for emergency services, millions of consumers and businesses.

Telstra chief operating officer Kate McKenzie said a core node, which provides services to a large area, was malfunctioning and improperly switched off by an engineer who failed to follow standard procedure. This in turn triggered a cascade failure as customers were shunted onto other nodes.