Labour's spokeswoman for police says a mistake by the country's crack crime fighting unit is not good enough.

A blunder by a staff member at the Organised and Financial Crime Agency has caused top-secret files to end up in the hands of criminals.

Jacinda Ardern says the error has put police informants and investigations in jeopardy.

"Whilst human error is something that we all have to contend with, in these kinds of cases there just isn't room for that..particularly when it comes to people being put at risk"

Police say processes have been changed since the incident, but Jacinda Ardern says it is alarming that adequate processes were not already in place to prevent it happening at all.