The Green Party says police need to explain evidence given by a senior officer at a court hearing into the monitoring of Kim Dotcom.
The German national, who has New Zealand residency, is fighting extradition to the United States to face copyright, money laundering and fraud charges.
A report by the Inspector-General of Intelligence and Security and retired judge Paul Neazor, which was released on Thursday, says the Government Communications Security Bureau (GCSB) relied on incorrect police information about Mr Dotcom's residency, believing him not to be a resident, and did not check further when it intercepted his communications.
During a court hearing regarding Mr Dotcom in August, Inspector Grant Wormald said that no one other than police were spying on the internet entrepreneur.
Greens co-leader Russel Norman is calling for a full inquiry into the matter and says police must explain the inconsistency.
"This is one of their senior officers giving inconsistent evidence under oath - that's a pretty serious matter. In the first instance, let's see how the police deal with that, but clearly they do need to deal with it."
In a statement, Police Commissioner Peter Marshall expressed confidence in the officers involved.
PM expects better performance
The Prime Minister says there will be changes in systems following mistakes by security agencies in monitoring Kim Dotcom.
John Key says a "brain fade" by an individual was responsible for possible breaches of the law, rather than a conspiracy, and he will be requiring better performance from the GCSB in future.
"The simple facts of life are that they suffered what can only be described as a massive brain fade by one person who actually reviewed the file.
"Now that's wrong and it shouldn't have happened, but people do make mistakes. It's not good enough and we'll put in place other systems to protect us in the future."
Mr Key says he does not believe a further inquiry is necessary, as Justice Neazor has already conducted one.