Ministers have announced an urgent review of KiwiRail after major disruption to train lines in Wellington this week.
Train services in the capital were drastically cut back after the breakdown of a specialist rail track evaluation car.
It prompted speed restrictions of 70kmh, with just half as many services as usual during peak times.
Transport Minister Michael Wood today called KiwiRail to the Beehive to provide an explanation on what happened and the plan to fix it.
In a statement this afternoon he said the disruption was "not good enough and follows other similar instances of service disruptions to commuters on KiwiRail's network".
"KiwiRail have accepted responsibility for the missteps which will result in further disruptions to services this week, and have reassured me they are acting quickly to restore fully functional services for commuters."
State Owned Enterprises Minister Duncan Webb said he had ordered an independent review into the operator, which would look into causes of the disruption across the country but largely focus on Wellington and the maintenance problems with the safety equipment.
Webb expected to appoint a reviewer this week, with findings to be reported next month, saying the review was "vital to public confidence".
The government had invested $8.6 billion into the rail network since 2017, with much of that going towards replacing track, installing new culverts and bridges, and upgrading turnouts, he said.
The government last week also announced 18 new trains for the Wairarapa and Kāpiti Coast lines to support express peak services and attract more commuters.