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(CNN) —  

Sen. Chuck Grassley, the chamber’s most senior Republican and a long-time defender of whistleblowers, rebuked President Donald Trump on Tuesday when he said that the individual behind a complaint at the center of House Democrats’ impeachment inquiry “appears to have followed the whistleblower protection laws and ought to be heard out and protected.”

Trump and his allies in recent days have repeatedly maligned the whistleblower’s motives and pushed to reveal the individual’s identity.

“Like every American, I deserve to meet my accuser, especially when this accuser, the so-called ‘Whistleblower,’ represented a perfect conversation with a foreign leader in a totally inaccurate and fraudulent way,” Trump said on Twitter over the weekend.

Earlier on Tuesday, Trump tweeted again about wanting to know the whistleblower’s identity, asking, “Why aren’t we entitled to interview & learn everything about the Whistleblower, and also the person who gave all of the false information to him.”

Grassley did not explicitly mention Trump in his statement but the senator offered a clear denunciation of the approach the President has taken since the complaint came to light.

“No one should be making judgments or pronouncements without hearing from the whistleblower first and carefully following up on the facts,” he wrote. “Uninformed speculation wielded by politicians or media commentators as a partisan weapon is counterproductive and doesn’t serve the country.”

The complaint shares concerns that Trump abused his office by seeking interference from a foreign country in the 2020 presidential campaign, asking Ukrainian President Volodymyr Zelensky for help digging up damaging material on former Vice President Joe Biden. The document also alleges that White House officials tried to cover it up by storing the record of Trump’s July phone call with Zelensky in a system for sensitive information, rather than the system where such records were usually kept.

Grassley, who chairs the Senate Whistleblower Protection Caucus and has worked extensively on whistleblower protection laws during his time in Congress, also pushed back on the notion that the complaint should be discarded because it consists of secondhand information.

“When it comes to whether someone qualifies as a whistleblower, the distinctions being drawn between first- and second-hand knowledge aren’t legal ones,” Grassley said. “It’s just not part of whistleblower protection law or any agency policy. Complaints based on second-hand information should not be rejected out of hand, but they do require additional leg work to get at the facts and evaluate the claim’s credibility.”

The whistleblower drew from more than half a dozen officials, according to the declassified version of the complaint.

Some of Grassley’s Senate GOP colleagues have also attacked the accuracy of the complaint: South Carolina Sen. Lindsey Graham said on CBS over the weekend that it “seems to be like a political setup.”

“It’s all hearsay,” Graham said. “You can’t get a parking ticket conviction based on hearsay. The whistleblower didn’t hear the phone call.”