Researchers say there is increasing evidence of what it calls unethical alliances between bloggers, politicians, media and public relations companies.
The Journalism, Media and Democracy research centre at AUT University says the boundaries between those groups are blurring.
The report highlighted what researchers said were major revelations in Nicky Hager's book Dirty Politics, and said they cast a shadow over long-established media organisations.
"After the revelations in Nicky Hager's book Dirty Politics, it appears that blogs are not necessarily a counterweight to commercial media outlets.
"The capability of blogs to retrieve the principles of public interest journalism became questionable. This report finds increasing evidence of unethical alliances among bloggers, politicians, PR companies and legacy media," the report said.
It also said there was more evidence this year that companies were under the control of fund management companies and unlisted financial institutions.
"During 2014 it became evident that New Zealand media corporates were facing increasing commercial pressure due to market and audience fragmentation.
"They were also becoming more profit-focused as their financial shareholders exerted influence.
"New Zealand commercial media corporations are mostly owned by fund managers, banks and wealthy media moguls who are prepared to restructure whenever necessary."
The report said the pursuit of profits was concerning because media companies were more vulnerable to restructuring.