Senator Lamar Alexander (R-Tn.) on Wednesday joined a group of 45 senators in a letter personally calling on President Obama to have his administration “comply with all requests” by Congress as it examines the Internal Revenue Service’s admitted targeting of conservative groups and others during the 2012 election.

“The First Amendment protects the rights of the American people to organize and speak up and speak out, and the IRS has violated those rights by creating what sounds like an enemies list to keep people quiet,” Senator Alexander said after joining the letter. “Congress needs to investigate the IRS’s actions to make sure something like this never happens again, and the Obama administration owes it to the American people to help us get to the bottom of this.”

n the letter, the senators say the IRS is guilty of “wholly inappropriate action that threatens to silence political dissent and brings partisan politics into what used to be a nonpartisan, unbiased and fact-based review process.” The letter demands that the administration “comply with all requests related to Congressional inquiries without delay,” including making IRS employees available.

Senator Alexander previously joined 11 senators in March 2012 in sending a letter to IRS commissioner Douglas Schulman seeking assurance that the agency’s string of inquiries toward 501(c)(4) organizations affiliated with the Tea Party “has a sound basis in law and is consistent with the IRS’s treatment of tax-exempt organizations across the spectrum.”

Senator Alexander said at the time, “The extra scrutiny the IRS appears to be giving Tea Party-related nonprofits is disturbing, so I hope we find that the IRS is treating all tax-exempt organizations the same. The government should not have what amounts to an enemies list based on what people or organizations say or believe, and if it turns out the IRS is denying Tea Party groups the proper tax status because of what they have to say, it must stop and those responsible must be held accountable.”