The Megaupload founder was one several people testifying at legislative intelligence committee hearings on proposed changes to the law covering the Government Communications Security Bureau.
Dotcom said he was a victim of abuse of surveillance powers that caused damage to his property, reputation and freedom.
"It is an injustice that I continue to fight every day," he said. "These abuses should never happen again."
The government drafted the amendments after the bureau was found to have overstepped its powers and spied on Dotcom illegally.
The German expatriate, who has New Zealand residency, tweeted a photo of himself with his wife and children leaving their Auckland home by helicopter for the hearing in Wellington.
Dotcom is on bail awaiting an extradition hearing to the US to face changes of internet piracy stemming from his file-sharing site.
His appearance included a long-awaited confrontation with Prime Minister John Key, who had been forced to apologize to him after a 2012 court ruling invalidated the search warrants used to seize his property.
The two had several verbal tussles during the hearing, with Dotcom insisting he had been promised 25 minutes to speak while Key said he would get only the same 15 minutes as other speakers.
The extradition hearing for Dotcom has been delayed several times.
"We remain certain we will not be extradited, and propose to live in New Zealand with our families for the foreseeable future," he said.