There's some concerns about cost blowouts on the new Cook Strait ferries, but Minister Chris Bishop isn't too worried.

A Treasury briefing from September warned of risks costs could overtake the budgeted $1.8 billion dollars.

Associate Finance Minister Chris Bishop says the Government's working at pace on this project and the new ferries are on their way.

"It's going to be tight, there's no doubt about that. But things are going pretty well." 

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