The probe into the Rev. Al Sharpton’s finances intensified this week, with the IRS sending out a flurry of subpoenas to his most generous corporate donors, The Post has learned.

Anheuser-Busch, the brewer of Budweiser and Michelob, confirmed yesterday that it received a federal subpoena in connection to its charitable giving to Sharpton’s National Action Network.

“We have received a subpoena and are cooperating with the IRS,” the company said in a statement.

Sharpton blasted the subpoena as a “fishing expedition” and said his donors are proud of their financial support. The St. Louis-based corporation donated between $100,000 and $499,000 to NAN in 2007 alone, according to its Web site, but declined further comment about its relationship with Sharpton. A knowledgeable source said several other corporate donors received or would soon receive subpoenas.

Sharpton himself, his business entities and his nonprofit civil-advocacy group owe millions in back taxes, documents show.

The IRS and the US Attorney’s Office in Brooklyn have an ongoing probe into Sharpton’s finances going back to his 2004 run for president and stewardship of NAN.

Last year, state Attorney General Andrew Cuomo began a probe of NAN because it failed to follow state financial-disclosure regulations for nonprofits.

Cuomo’s office has since turned over its NAN file to the US Attorney’s Office.

As of 2006, the most recent year that financial documents for the group are publicly available, it owed $1.9 million in payroll taxes and penalties.

Ten NAN staffers were slapped with subpoenas this past December, and the Anheuser-Busch subpoena is part of the same probe.

News of the fresh subpoenas comes just days after The Post chronicled Sharpton’s relationship with some of the country’s largest corporations.

Sharpton threatened boycotts or protests against corporations while simultaneously soliciting donations and sponsorships of NAN events, The Post detailed.

Personally, Sharpton owes $931,397 in federal taxes and $365,558 in New York City taxes, according to an IRS lien.

The controversial reverend characterized the latest move by the feds as harassment.

“I think that this is a clear, transparent political investigation, because if they started an investigation in December, why would they be subpoenaing people after December unless they are on a fishing expedition?” Sharpton said.

“Most of my annual donors had already spoken to the IRS when we did audits. We do audits every year.”

The IRS and US Attorney’s Office declined to comment.

Additional reporting byStefanie Cohen

cbennett@nypost.com