The Auditor-General says the Ministry for Primary Industries is under-prepared for biosecurity incursions.
Lyn Provost's report into how the ministry is preventing the establishment of foreign pests makes particular recommendations for high-risk organisms, such as the livestock disease foot and mouth.
The report says the ministry is too focused on responding to incursions rather than preparing for the potential arrival of pests and diseases.
It says the current plan for dealing with a foot and mouth outbreak is inadequate and the ministry should have a regular testing and simulation programme.
Foot and mouth is one of the world's most infectious diseases of farmed animals. It is estimated that an outbreak would cost New Zealand $8 billion in its first year.
The Auditor-General's office manager, Gary Emery, says if a foot and mouth outbreak was to occur, the main concern would be around testing for the disease, distributing the vaccine and carcass disposal.
The Government said on Thursday it would carefully consider the Auditor-General's recommendations.
Primary Industries Minister Nathan Guy said continuing to improve biosecurity is his top priority. He said the Government is conscious of how important it is to protect the border and believes a large amount of work has gone into planning for foot and mouth disease.
But the Labour Party says the critical report on biosecurity preparedness is a reflection of the Government's spending cuts.
Leader David Shearer said the Government's slash-and-burn approach to public money has undermined the Ministry for Primary Industries.
"They've cut money from their budget, they've taken out frontline staff, they're not prepared for an incursion should it occur - it's a disaster.
"What the Government has done has taken its eye completely off the ball of what is most important, which is protecting our environment from incursions."