A coalition of more than a dozen progressive groups announced plans today for an aggressive campaign to pressure corporations and big donors to stay out of politics.

“We are saying to corporate America: Enough is enough,” said New York Public Advocate Bill de Blasio at a press conference at the Service Employees International Union headquarters that brought together a broad range of good-government, consumer and civil rights groups.

Organizers said they will use consumer boycotts, shareholder resolutions, legal actions and public pressure to target both big individual and corporate donors. The campaign will focus on contributors to super PACs as well as to nonprofits and trade associations that are not subject to disclosure rules.

One coalition member, Americans United for Change, announced a $25,000 reward for the first employee who “blows the whistle” on a corporate employer’s use of treasury money to influence the election through a non-disclosing entity such as a politically active nonprofit. Said de Blasio: “Every tool is on the table today.”

The multipart campaign builds on an anti-corporate-money movement that’s been gaining steam since the 2010 Citizens United ruling lifted restrictions on direct corporate and union spending in campaigns.

A corporate reform coalition that includes shareholders and corporate accountability advocates is pushing the Securities and Exchange Commission to require corporations to disclose political spending to shareholders. Corporate watchdogs have also partnered with shareholder organizations to write letters to hundreds of CEOs and to file proxy resolutions calling for more disclosure.

“Each of these resolutions will go to the vote this spring,” Common Cause President Bob Edgar said. He added: “We plan to let corporations know that there will be a great cost in playing politics.”

Organizers pointed to embarrassment and policy changes at companies such at Target Corp., which faced a backlash in 2010 after a controversial political expenditure.

But the group’s challenge is that the bulk of contributions to unregulated super PACs, for one, comes from individuals and not corporations. Direct corporate contributions accounted for only 17 percent of super PAC contributions in 2010 and 2011, according to a recent study by the U.S. Public Interest Research Group. By contrast, 56 percent of the money came from individual big donors, typically the CEOs of real estate, financial services and energy companies.

Asked how the campaign would target individual donors, who do not face direct shareholder pressure, de Blasio noted that even individuals care about their companies’ public image.

“There are a lot of pressure points, even in less-well-known corporations,” he said, adding that the campaign would also focus on state and local governments and on the stock holdings of public pension funds. De Blasio is a member of the board of the New York City Employee Retirement System.

Though the press conference took place at the SEIU headquarters, no SEIU representative shared the stage or the microphone with other coalition members. Labor unions, too, have been freed up by the Citizens United ruling and are expected to spend heavily in the 2012 election.

Asked whether organizers would go after labor union spending, too, as well as Democrat-friendly nonprofits, de Blasio said the campaign would target “every kind of organization” and “both sides of the spectrum.”

Coalition members in attendance also included the Campaign for America’s Future, the Coalition for Accountability in Political Spending, Every Child Matters, Health Care for America Now, the Leadership Conference on Civil and Human Rights, MoveOn.org, the National People’s Action, Occupy Wall Street, Progress Now, Public Campaign Action Fund, Public Citizen, USAction and U.S. PIRG.