Telecom engineers investigating internet irregularities weeks before GCSB has said it started spying on him.
Kim Dotcom's internet connection was being diverted inside New Zealand weeks before the Government Communications Security Bureau says it started spying on him.
The Herald has obtained details showing Telecom engineers and staff at its technology services company Gen-I were investigating irregularities with his internet connection in November.
The revelation has raised suspicion that Mr Dotcom was victim to earlier spying than the GCSB has admitted. It has brought fresh calls for an inquiry amid claims of the spy agency's role in the international "Five Eyes" Echelon Network.
The focus of the early investigation is the dedicated internet connection from Mr Dotcom's mansion in Coatesville to the Sky Tower in Auckland. It was intended to give him the fastest possible internet connection - a factor which would have been critical in his quest to be the best in the online Modern Warfare 3 game.
Mr Dotcom became the "number one" ranked player of the game before his arrest.
During the record-setting effort, Gen-I staff began an investigation into the amount of time it took for an internet signal from Mr Dotcom's home to reach an offshore Xbox computer server.
Information held by the Herald shows Gen-I studied data showing the amount of time it took information on the internet connection to reach the Xbox server. It went from 30 milliseconds to 180 milliseconds - a huge increase for online gamers.
The reason for the extra time emerged in a deeper inquiry, which saw a "Trace Route" search which tracks internet signals from their origin to their destinations. When the results were compared it showed the internet signal was being diverted inside New Zealand.
The data showed the internet signal had previously taken two steps before going offshore - but was now taking five.
The GCSB is under police investigation after admitting it illegally spied on Mr Dotcom between December 16 and January 20, the day of the raid. It is also studying three other cases of possible illegal action carried out after requests from the police.
The other cases emerged after Prime Minister John Key - who is responsible for the agency - ordered an inquiry. Asked about the possibility of earlier spying, a spokeswoman said the Prime Minister had sought and received "a fresh assurance" the GCSB and Security Intelligence Service had not carried out any surveillance before December 16.
Green co-leader Russel Norman said it could not be ruled out.
He said a commission of inquiry was needed to examine the behaviour of the GCSB.
He said it could be conducted in secrecy with sensitive material excised from a final public report.
Mr Norman highlighted the Echelon of Five Eyes agreement where the GCSB worked with intelligence agencies from the US, Australia, Canada and the UK.
Labour leader David Shearer said he also wanted an independent inquiry which could be run by a senior and trusted New Zealander. "The critical issue is who knew what and how all the checks and balances work."
A Telecom spokeswoman said the company would not give information to the police of "any other government agency" unless legally forced to do so.