WASHINGTON (AP) ― America’s national and local public broadcast stations are hiring more journalists and pumping millions of dollars into investigative news to make up for what they see as a lack of deep-digging coverage by their for-profit counterparts.

Public radio and TV stations, funded by audience contributions, foundations, and some tax funds, have seen the need for reporting that holds government and business accountable increase as newspapers and TV networks cut their staffs and cable television stations have filled their schedules with more opinion journalism.

“Where the marketplace is unable to serve, that’s the role of public media,” PBS President and CEO Paula Kerger said last year at a summit on the future of media at the Federal Communications Commission. “PBS exists to serve the people, not to sell them.”

In the past three years, the Corporation for Public Broadcasting has invested more than $90 million in federal funds on new journalism initiatives. That includes a $10 million local journalism initiative that is paying for the creation of five regional centers that will help local PBS and National Public Radio (NPR) stations cover news that affects wider geographic areas. Also, a $6 million grant from the group expanded the PBS investigative series “Frontline” from a seasonal series with a summer break to a year-round program.

Meanwhile, NPR has started an investigative reporting unit supported by philanthropic funds ― including $3.2 million donated in the last year.

The need for such probing journalism was highlighted by a 2010 study by the Pew Project for Excellence in Journalism. It noted the “old model” of American journalism that supported watchdog reporting ― by valuing stories based on their significance over their individual popularity ― is breaking down. In new models driven by the Internet, revenue is more closely tied to individual stories and how popular they are, leaving less incentive for civic news.

Newsroom staffs also continue to shrink, the study found.

Still, the prospect of tax dollars going toward public stations’ journalistic efforts has already drawn criticism. Their push for more news reporting also comes as conservatives seek to cut all federal public broadcast funding as part of their budget proposal.

It’s a threat public broadcasters take seriously, though similar efforts in the 1990s and 2005 did not succeed.

Randolph May, president of the Rockville, Maryland-based Free State Foundation, argued at the FCC summit that government-funded media should not be involved in shaping public opinion.

“In an age of information abundance, we do not need, and should not want, government-supported media acting as a filter or a megaphone,” said May, whose group is nonpartisan but advocates for libertarian principles.

Patricia de Stacy Harrison, the head of the Corporation for Public Broadcasting, said she can take the heat for using public dollars for probing journalism, because it’s an important public service.

“Doubtless, if all of these people doing the jobs they’re supposed to do, our phones will be ringing, e-mail will be coming in,” Harrison told the Associated Press.

The corporation is the primary conduit for federal funds distributed to public media, and Harrison described it as a firewall.