"The privacy interests of donors is widely recognized and valued. Various public policy initiatives have rightly encouraged donations to social welfare organizations, and these efforts are threatened when private information about donors is not adequately protected," the letter states.

The new letter, from Sen. Orrin HatchOrrin HatchLive coverage: Senate GOP unveils its ObamaCare repeal bill Grassley doesn't see how Judiciary 'can avoid' obstruction probe Ryan calls for tax reform to be permanent MORE (R-Utah) and other GOP senators, says that, by requesting the confidential donor names, the agency has set in motion a process that will result in the names being available for public viewing at the IRS when the investigated groups are approved to become a 501(c)(4).

"The IRS appears to be circumventing the statutory privacy protections that Congress has long provided donors," exposing the donors to "possible harassment," the Republicans said."The public release of private donor information exposes citizens to possible harassment and intimidation by those who oppose the goals of the charitable organization."

Republicans and Democrats on Capitol Hill have been clashing over 501(c)(4) and other tax-exempt groups, some of which are spending millions of dollars this year on election advertising. 

The IRS currently says that the primary purpose of 501(c)(4) groups should not be political, which has led some legal analysts to assert that those organizations should use less than 50 percent of their budget on political causes.  

Watchdogs argue groups are misusing the 501(c)(4) tax-exempt status to keep their donors secret as they spend millions on election ads. 

The Republican senators requested that the IRS provide the statutory authority to require donor names, the frequency of requests for the information, and which officials were involved in requesting and approving the "questions requesting donor names," among other issues.

Along with Hatch, the Republican senators who signed the letter were Mitch McConnellMitch McConnellOpioid crisis threatens GOP ObamaCare repeal Trump making calls to senators on healthcare bill Trump called Cruz to press him on ObamaCare repeal bill: report MORE (Ky.), Mike EnziMike EnziBudget committee approves Trump's OMB deputy Senate GOP paves way for ObamaCare repeal bill Senate returns more pessimistic than ever on healthcare MORE (Wyo.), Lamar AlexanderLamar AlexanderThe Hill's Whip List: Senate ObamaCare repeal bill Trump administration pays June ObamaCare subsidies to insurers Republicans and the lost promise of local control in education MORE (Tenn.), John CornynJohn CornynOpioid crisis threatens GOP ObamaCare repeal Lawmakers want meeting with Trump administration to take US-Mexico border trade Rocky rollout for Senate healthcare bill MORE (Texas), Kay Bailey Hutchison (Texas), Jon Kyl (Ariz.), Bob CorkerBob CorkerPolicymakers forget duty to protect taxpayers from financial failures Overnight Defense: GOP chairman moves ahead with 0B defense bill | Lawmakers eye 355 ship navy | Senate panel seeks answers on shoot down of Syrian jet Overnight Cybersecurity: Trump tweetstorm on Russia probe | White House reportedly pushing to weaken sanctions bill | Podesta to testify before House Intel MORE (Tenn.), Pat RobertsPat RobertsThe Hill's Whip List: Senate ObamaCare repeal bill Meet Jay Sekulow, the new face of Trump’s legal team Overnight Healthcare: Senate GOP eyes July vote on health bill MORE (Kan.), John ThuneJohn ThuneSenate panel unveils aviation bill with consumer protections, drone fix Four Senate conservatives say they oppose ObamaCare repeal bill Live coverage: Senate GOP unveils its ObamaCare repeal bill MORE (S.D.) and Rand PaulRand PaulSunday shows preview: Senate healthcare debate heats up Trump called Cruz to press him on ObamaCare repeal bill: report Trump tells Democrats they need ‘courage’ to fix ObamaCare MORE (Ky.).

— Bernie Becker contributed to this report.