The top Republican on the House Judiciary Committee unloaded on the panel's chairman, Jerry Nadler, in a fiery letter on Thursday, accusing the New York Democrat of conducting an unconstitutional "inquisition" into President Trump and his associates "reminiscent of Eastern regimes during the Cold War."

Nadler, who would oversee any impeachment proceedings against President Trump, this week announced dozens of document requests -- including to the National Rifle Association (NRA), WikiLeaks and key figures in the Trump Organization -- in a barrage that Nadler called the opening salvo in new and wide-ranging investigations into the White House.

Georgia Republican Rep. Doug Collins, the ranking member on the committee, charged that Nadler's investigation runs "afoul of nearly 150 years of Supreme Court precedent and over 200 years of oversight conducted by this committee."

Collins previously told Nadler to "come back to reality" following his sweeping document requests -- and, in his letter on Thursday, he told Nadler to pay more attention to the Constitution.

Specifically, Collins wrote, "Congress can only exercise its oversight power with a valid legislative purpose in sight. Congress should not—and, according to the Supreme Court, cannot—conduct oversight for the sake of exposure alone. Absent a formal impeachment inquiry — which you have been clear your nascent investigation is not — oversight for the sake of exposure is exactly what your investigation appears to be doing.”

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Collins cited Watkins v. United States, a 1957 Supreme Court case that held “there is no general authority to expose the private affairs of individuals without justification in terms of the functions of the Congress.”

The Watkins Court, Collins added, also wrote a congressional inquiry “must be related to, and in furtherance of, a legitimate task of Congress.”

"Your 81 letters appear to be little more than a deep-sea fishing expedition with the purpose of exposing private matters and airing alleged dirty laundry rather than legislating," Collins told Nadler.

Nadler, who has said in televised interviews that he has already personally concluded that Trump "obstructed justice," initiated the requests on the heels of former Trump lawyer Michael Cohen's dramatic House testimony late last month.

During a public hearing before the House Oversight Committee, Cohen raised questions about the president's personal finances, his charity and more even as he testified he had no evidence of collusion with Russia.

"Because they serve no valid legislative purpose, these requests infringe on both the recipients’ protected speech rights and right to associate," Collins wrote to Nadler. "Instead, your requests are part of a concerted effort to target and punish associates of the president. This effort to intimidate those who choose to associate with the president 'through actual or threatened imposition of government power or sanction' violates the First Amendment."

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According to Collins, both the "depth and breadth" of Nader's inital investigative forays were "astounding" and "alarming."

"Were Congress to usurp the executive function of prosecuting crimes, this government would be on the cusp of a constitutional crisis," Collins concluded. "The provenance of your investigation, launched on the eve of the conclusion of the Special Counsel’s work and your request for documents already submitted to multiple prosecutorial bodies threatens to place this Committee in the untenable position of conducting public show trials for individuals not prosecuted by the special counsel’s office."

In a similar letter last month, Collins asked Nadler why the panel's Democratic leadership made what he called the "costly" and "unusual" decision this week to hire two prominent anti-Trump consultants to conduct a purportedly impartial investigation of the White House.

Fox News' Mike Emanuel contributed to this report.