Congressional investigators have uncovered emails showing ex-IRS official Lois Lerner targeted a sitting Republican senator for a proposed internal audit, a discovery one GOP lawmaker called "shocking."

The emails were published late Wednesday by the House Ways and Means Committee and pertain to the woman at the heart of the scandal over IRS targeting of Tea Party groups.

The emails appear to show Lerner mistakenly received an invitation intended for Sen. Charles Grassley, R-Iowa, in 2012.

The event organizer, whose name is not disclosed, apparently offered to pay for Grassley's wife to attend the event, which caught Lerner's attention. The December 2012 emails show that in response, Lerner suggested to an IRS colleague that the case be referred for an audit.

"Looked like they were inappropriately offering to pay for his wife. Perhaps we should refer to Exam?" she wrote.

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    Her colleague, though, pushed back on the idea, saying an offer to pay for his wife is "not prohibited on its face." There is no indication from the emails that Lerner pursued the issue any further.

    Republicans pointed to the exchange as yet another example of Lerner using her position in the Exempt Organizations unit to apply scrutiny to conservatives.

    "We have seen a lot of unbelievable things in this investigation, but the fact that Lois Lerner attempted to initiate an apparently baseless IRS examination against a sitting Republican United States Senator is shocking," Ways and Means Committee Chairman Dave Camp, R-Mich., said in a statement.

    "At every turn, Lerner was using the IRS as a tool for political purposes in defiance of taxpayer rights."

    Grassley said Thursday that he initially found out about Lerner's email request two months ago. He said that he could not talk about the organization that invited him because of taxpayer confidentiality, but that he did reject the invitation.

    Grassley said in a separate statement that this kind of incident fuels concerns people have about "political targeting" at the highest levels. "It's very troubling that a simple clerical mix-up could get a taxpayer immediately referred for an IRS exam without any due diligence from agency officials," the senator said.

    The IRS, in response to the publication of the emails, said in a statement that it could not comment on "any specific situation" due to taxpayer confidentiality issues.

    But the agency added: "As a general matter, the IRS has checks and balances in place to ensure the fairness and integrity of the audit process. Audits cannot be initiated solely by personal requests or suggestions by any one individual inside the IRS."

    The emails come at a sensitive time in the IRS targeting investigation. Congressional Republicans are furious after learning earlier this month that a trove of Lerner emails have disappeared, apparently after a 2011 hard drive crash.

    IRS Commissioner John Koskinen has been called to testify twice on Capitol Hill since last week on the lost emails.

    Camp said in his statement: "We may never know the full extent of the abuse since the IRS conveniently lost two years of Lerner emails, not to mention those of other key figures in this scandal."

    Grassley, incidentally, is a member of the Senate Finance Committee -- which is one of the congressional panels investigating the IRS over the targeting scandal.

    Rep. Charles Boustany, R-La., told Fox News that the revelation that Lerner tried to scrutinize Grassley over an invitation is another example of the administration using the agency as a "political tool, as a weapon."

    Fox News is told that Grassley did not end up attending the speaking engagement in question, which was supposed to be in the spring of 2013.

    As for how Lerner got the invite intended for Grassley, a source said it was only a "weird coincidence."

    Fox News' Chad Pergram and The Associated Press contributed to this report.