Calls are growing for an investigation into the ongoing problems the Cook Strait ferries have faced.

The current fleet has been hit hard by mechanical failures and KiwiRail has said it will be impossible to get any new Interislander ferries in until 2025.

Transporting NZ CEO Nick Leggett says the KiwiRail's current model is unsustainable, and the lack of certainty is 'upsetting' for people.

Nick Leggett says the Government needs to weigh in here to encourage KiwiRail to come up with a long-term plan.

LISTEN ABOVE

• Would-be Cook Strait ferry passenger on Interislander's lack of communication
• Ferry nightmare for passengers as another sailing cancelled
• Interislander ferry to resume passenger sailings after mayday
• 'A little bit of love' needed for Cook Strait ferry staff