Prompting calls to Iowa GOP Sen. Chuck Grassley’s office from a smattering of angry evangelicals, preacher Kenneth Copeland penned a February letter to followers slamming the Senator’s probe into alleged financial improprieties by six ministers.

“The enemy is not going to steal what the Lord has won through his ministry, and he is not going to use this attack to bring harm to the rest of the churches and the ministries in America!” reads the four-page missive.

The letter is signed by Copeland, who is pastor along with his wife, Gloria, of the massive Kenneth Copeland Ministries based in Newark, Texas. Copeland recently made political headlines when he raised as much as $100,000 for GOP presidential contender Mike Huckabee, a Baptist minister.

Copeland’s ire is directed at a Congressional probe examining alleged financial mismanagement at six high-profile churches spearheaded by Grassley, the ranking member and former chairman of the Senate Finance Committee.

“Sen. Grassley’s office received very roughly three dozen calls from Mr. Copeland’s supporters in reference to the letter, echoing the sentiments expressed in the letter,” a Grassley spokeswoman said on Monday.

“If the callers had had the opportunity to hear Sen. Grassley’s perspective, they might have had a different viewpoint.”

In his letter, which comes on the heels of a fiery sermon preaching similar opposition, Copeland rails that Grassley’s probe threatens other churches and pastors, though it’s unclear to whom the missive was mailed.

“If KCM [Kenneth Copeland Ministries] fails to defend its legal rights, then we are deeply concerned that you , or your neighbor’s church, will be next,” Copeland warns. “And because of that, I give you my word that we will not waver.”

Grassley is investigating allegations of financial mismanagement and lavish lifestyles, including homes and exotic trips, involving pastors of six high-profile evangelical churches across the country. The churches are tax-exempt organizations and thus do not have to file Form 990 with the Internal Revenue Service.

But his interest in what the churches argue is private information has raised eyebrows among some conservative Republicans with ties to the evangelical community. They fear it may further divide the Republican base during a hotly contested presidential election.

Former Rep. Bob Barr (R-Ga.), now practicing law in Atlanta, wrote a November opinion piece in the Atlanta Journal-Constitution criticizing Grassley and saying he must have “forgotten” he is no longer Finance chairman.

“If people buy into a church and want to provide money for the pastor to maintain a certain lifestyle, it hardly seems fair or appropriate to me that some Congressman or Senator … should take umbrage at that,” Barr said Monday.

Some of the ministries show signs of cooperating. In a new development, representatives of Benny Hinn’s World Healing Fellowship “provided a significant amount of written material” to Grassley’s office on Monday, according to Grassley’s spokeswoman. Hinn is one of the better-known pastors whose finances are being examined, and his decision could sway others to cooperate with the Senator.

Joyce Meyer of Joyce Meyer Ministries in Fenton, Mo., has “substantially” answered Grassley’s queries, according to his staff, which has a follow-up meeting scheduled with church officials this week.

But Copeland, and two of the other ministers, have taken a more aggressive tack. In the letter, Copeland repeats that he will go to jail rather than turn over information about donors and partners.

In Copeland’s letter, he says the church did provide Grassley with 23 pages of answers and 291 pages of exhibits, but Grassley’s office calls their response insufficient.

“I have instructed everyone working on behalf of KCM that we will follow what that scripture commands us to do: Give those things which are rightfully the government’s to the government and to the governmental agency to which it belongs — in this case [the IRS],” Copeland writes. “But as to those things which may be God’s, they shall be God’s and no one else’s, so help me God!”

Creflo Dollar of College Park, Ga.-based World Changers Church has said he will not turn over information without a subpoena, and Eddie Long of New Birth Missionary Baptist Church in Lithonia, Ga., has not complied.

Grassley is preparing a second set of letters to the ministries to follow up on his original Nov. 15 request. But the Senator has little legal leverage without issuing a subpoena, something he can’t do without the support of Finance Chairman Max Baucus (D-Mont.).

“Sen. Grassley’s investigators continue to keep open the lines of communication with the ministry, while also considering additional steps in the Congressional review,” the Grassley spokeswoman said.

Grassley sees the investigation into the churches’ finances as a logical extension of his wide-ranging probe into nonprofits, which has included The Nature Conservancy, the Smithsonian and the Red Cross.

But Copeland seems to view the probe as an attack on Pentecostal churches with charismatic leaders like himself. In the second paragraph of the letter, Copeland points to the fact that the six churches being investigated “all preach the Word of Faith” message. Grassley is a Baptist.

The six churches preach a message known as a “Prosperity Gospel” in which God is said to encourage earthly success and riches.

But Grassley has stressed that the probe has nothing to do with religious faith, and he has said he will endeavor to keep appropriate financial information private. “The federal treasury forgoes billions of dollars a year in revenue to tax-exempt groups, while the taxpayers fund government functions,” his spokeswoman said.