A key lawmaker is seeing red over all the black ink being spilled by the FBI redacting text messages between two FBI officials involved in the bureau’s probe of Hillary Clinton’s email server.

Sen. Ron Johnson, R-Wis., who chairs the Homeland Security and Government Affairs Committee, fired off a pointed letter last week to FBI Director Christopher Wray objecting to what he called "excessive redaction of documents” that he claimed were hindering his committee’s oversight role.

In the June 8 letter, Johnson repeated a familiar GOP charge that the bureau and the Department of Justice were withholding and redacting critical information to protect their agencies from embarrassment.

"These reviews showed highly questionable redactions without apparent legitimate reasons," Johnson wrote.

The text messages are part of a trove of thousands sent between FBI agent Peter Strzok and his lover, former bureau attorney Lisa Page. GOP investigators believe the texts shed light on efforts by some within the bureau to exonerate Clinton of mishandling classified material and possibly to mount a dubious probe of President Trump.

Johnson’s letter followed an “in camera,” or supervised review by committee staff of unreleased, more complete documents and emails which were still partially redacted.

Prior to his demotion to the FBI’s Human Resource department, Strzok was a key member of the bureau’s counter-intelligence team investigating Clinton’s use of a private server for government business conducted while she served as secretary of state. After former FBI Director James Comey’s controversial July 5, 2016 press conference -- at which he declared Clinton’s actions “exceedingly reckless“ but recommended against criminal charges -- Strzok was assigned to Special Counsel Robert Mueller’s investigation into alleged Russian collusion with the Trump campaign.

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Page, who was a close adviser to fired Deputy FBI Director Andrew McCabe, resigned from the FBI in May.

The texting lovers’ relationship was exposed by DOJ Inspector General Michael Horowitz, who is concluding a sweeping review of the department’s handling of the Clinton probe. The pair’s relationship and motivation are expected to factor into Horowitz’s report, slated for release Thursday.

Johnson detailed several concerns about FBI redactions in his letter.

“These redactions included the names and what appears to be initials of Justice Department or FBI employees,” Johnson wrote. “Redacting the identities of these employees prevents the Committee from assessing the need to request additional documents relating to these employees or requesting interviews with these employees.”

Johnson faulted the FBI and DOJ for not providing a reasonable basis for making the redactions. He referred in particular to a redacted, Aug. 5, 2016 text from Strzok that states "the White House is running this." According to Johnson’s committee, the "unredacted version appears to attribute the quote to an individual with the initials L.C." It is unclear who "LC" is.

In an Oct. 11, 2016 email, Strzok wrote that he is "currently fighting with [redacted]” over a FISA issue. The unredacted version revealed by Johnson's letter to the Wray fills in the redaction to reveal the redacted name as “Stu" It is unclear who “Stu” is.

Days before the 2016 presidential election, in a newly unredacted exchange, Strzok also writes that “I am still angry at them over this stupid BO DOD thing.” Fifteen minutes later, Strzok texts Page again stressing that he is “Just cranky at them for bad choice about BO.”

It is unclear who BO is, though DOD may refer to the Department of Defense.

"My whole point of my investigation -- we've been doing this for three years now -- is to make the public aware full disclosure so that the FBI and the DOJ can regain their integrity, the credibility which it needs to serve the American public,” Johnson said in an interview with Fox News.

Fox News’ Catherine Herridge contributed to this report.