Telecom staff were working through the night to try to restore service on its troubled XT mobile phone network after the system crashed again yesterday, company spokesman Mark Watts said.
From about 4pm, as many as 200,000 users south of Taupo were unable to make or receive calls, with text messaging and data transfers affected "to a lesser extent", Mr Watts said.
"We are in crisis meetings right now and are furiously attempting to fix things," he said at 8.30pm.
"We are appalled and disappointed customers have been affected again and will be working through the night to try and restore service as quickly as possible."
The fault was on the same part of the network which crashed for 11 hours in December and for almost three days last month.
Text services in the lower part of the South Island were also intermittently affected on two days last week.
The network was launched in May last year to great fanfare, but the embarrassing breakdowns have already cost Telecom more than $5 million in compensation packages and have required public apologies from chief executive Paul Reynolds.
Yesterday's crash occurred just hours after the system problems claimed their first scalp.
Alcatel-Lucent, the company responsible for installing the network, issued a statement earlier in the day saying New Zealand chief executive Steve Lowe would be replaced on March 8 by Jyoti Mahurkar-Thombre.
