Telecom’s email cyber attack is four times worse than first thought.

Last weekend 20,000 Xtra accounts were compromised as a result of a security breach at outsourced email provider Yahoo. Users’ address books were mined and spam sent out to their contact lists.

Since the system was hacked 60,000 of Telecom’s 450,000 customers had changed their passwords voluntarily.

The company had also been contacting 15,000 customers whose accounts were compromised.

But with accounts still being hacked, the company tonight axed the passwords of an addition 60,000 users - bringing the total number of affected clients to about 80,000.

A spokesperson said Telecom hoped the figure wouldn’t climb further, but was relying on Yahoo to identify affected accounts.

"The move by Telecom is aimed at protecting its email customers and preventing information contained within their emails being accessed although to date there is no confirmed evidence, by Yahoo!, that this has occurred," a statement on its website said.

To unlock their account users needed to select a new password at telecom.co.nz.