National MP John Carter has criticised Slingshot for the way it convinced his 86-year-old mother to transfer a home home line to their service.

New Zealand's government isn't trying to undermine Telecom by bolstering rural broadband services, Communications Minister Steven Joyce says.

Telecom's stock price hit an all-time low yesterday after it told the market that its share of the Government's new rural broadband initiative would cost it $168 million over three years.

A proposed optic fibre cable linking NZ, Australia and the USA would unleash billions of dollars of economic potential by connecting NZ businesses to global markets by 2013.

Vodafone says it is "fully focused" on ensuring the patchy service does not happen again.