The network has been plagued with problems since being introduced late last year, with an outage affecting customers south of Taupo yesterday.
It is the fourth time since Christmas customers have been unable to rely on their phones and there have been reports that some also failed to get through to the 111 emergency line.
Transport Minister Steven Joyce voiced concerns over the reports but said Telecom was a private company.
"It is for them to look after their customers and deliver their service. The Government's job in this situation is firstly to make sure where we can that the 111 system is operating effectively and I sought assurances from Telecom last night and officials are following up with them today on that issue."
Mr Joyce said the Government was concerned, but: "I can't add any more pressure on to Telecom than their customers will already being placing on them. They will be very very well aware of that".
Mr Joyce said the problems were embarrassing for the company and were bad timing in terms of contract possibilities.
Mr Goff said the Government should be demanding action.
"I think it is remarkable that a minister is sitting on his hands while a major infrastructure network has collapsed four times. He has got to get in there, demand explanations and demand remedies. He owes that to the country, the security issues around 111 and also to the customers who are being deprived of what they should reasonably expect," Mr Goff said.
"There has to be a clear government responsibility over the provision of major infrastructure services when it relates to safety."
The Dominion-Post website reported calls to 111 after a student was attacked at a Christchurch mall failed to get through.
Witnesses said an Asian student was left beaten and bloodied after the assault by four skinhead youths at a bus stop outside the Palms Mall in Shirley about 6.30pm yesterday.
Mr Joyce said he had not been told about the incident but he had sought reassurance about the 111 service yesterday when he spoke to Telecom boss Paul Reynolds.
"I am concerned and that is why I asked last night without any knowledge of that situation if Telecom could provide assurances that people could call 111 from their XT phones... Officials are following that up today and will seek further assurances."
He said Telecom should be able to guarantee the 111 service worked "as much as technically possible, yes".
Dr Reynolds said today he had accepted the resignation of his IT chief Frank Mount.
His is the second departure in the wake of the series of XT outages, with Alcatel-Lucent, the partner of Telecom which built the XT network, yesterday announcing that its New Zealand chief executive, Steve Lowe, had resigned.
Mr Mount was appointed in May 2008, when Dr Reynolds said he would play a key role in delivering a "new generation of world-class services".
The resignation had been accepted with regret but in the interest of customers and the company, he said today.
