The Electoral Commission says it warned internet entrepreneur Kim Dotcom that his birthday and album release party could break electoral law.
On Thursday afternoon, Mr Dotcom cancelled the free party for about 25,000 people scheduled for Auckland's Vector Arena on Monday.
The birthday bash was originally intended to include details about his planned political party, the Internet Party, which will contest this year's general election.
However on Wednesday, Mr Dotcom tweeted that those details would be released on a separate day at another event.
The Electoral Commission says it emailed Mr Dotcom's legal representative that night, saying despite attempts to distance the event from his political movement, Monday's party could still be seen to be influencing voters.
The commission warned it could expose those promoting and attending it to the risk of prosecution.