Senate Minority Leader Chuck Schumer (D-NY) on Monday demanded Republican lawmakers launch an investigation into the so-called whistleblower complaint regarding a telephone call between President Donald Trump and a foreign leader.

In a letter to Senate Majority Leader Mitch McConnell (R-KY), Schumer urged Republicans to “fulfill your constitutional duty” by probing the complaint, which is believed to center around President Trump allegedly urging Ukraine leader Volodymyr Zelensky to look into former vice president Joe Biden’s scandals in the Eastern European country.

“In the face of this dire warning and the Trump Administration’s effort to cover it up, the Republican-led Senate has remained silent and submissive, shying away from this institution’s constitutional obligation to conduct oversight,” Schumer wrote.

“The Republican Senate’s ‘see no evil, hear no evil’ attitude toward such a serious national security concern is unacceptable and must change,” he added, before calling on McConnell to hold hearings and issue a subpoena for the complaint.

House Intelligence Committee members were briefed last week by Joseph Maguire, the acting Director of National Intelligence, about the complaint, though the official would not provide specifics to lawmakers or comply with panel chair Adam Schiff’s (D-CA) demand that he turn over the complaint, due to executive privilege.

Buried in establishment media’s reportage on the complaint is the fact that the so-called whistleblower did not have “direct knowledge of the communications.”

Speaking Sunday to reporters, President Trump said his conversation with Zelensky was “largely congratulatory,” adding that he did mention how he does not want people like Biden and his son contributing to “the corruption already in the Ukraine.”

“When the president speaks to the head of another country, he has to be able to speak to those people and those people don’t want to know that they’re being recorded or that you have a stenographer working,” the president said ahead of a trip to Houston, Texas, with Indian Prime Minister Narendra Modi. “You don’t want to have to hear that. You can’t do that to a president and you can’t do that to other countries.”

Ukraine’s Foreign Minister Vadym Prystaiko has also dismissed the notion of any wrongdoing in President Trump’s called with Zelensky, telling Hromadske, a Ukrainian online broadcast outlet, “I know what the conversation was about and I think there was no pressure.”

“There was talk, conversations are different, leaders have the right to discuss any problems that exist. This conversation was long, friendly, and it touched on many questions, sometimes requiring serious answers,” Prystaiko added.

Though there is still much unknown about the so-called complaint, House Democrat leaders such as Schiff, and even House Speaker Nancy Pelosi (D-CA), have suggested the Trump-Zelensky call could be grounds for impeachment.

“If the Administration persists in blocking this whistleblower from disclosing to Congress a serious possible breach of constitutional duties by the president, they will be entering a grave new chapter of lawlessness which will take us into a whole new stage of investigation,” Pelosi wrote to lawmakers on Sunday.

Appearing on CNN’s State of the Union, Schiff (D-CA) said Sunday that impeachment may be “the only remedy” as President Trump confirmed he discussed Biden and corruption with Ukraine’s president.

“If the president is essentially withholding military aid at the same time that he is trying to browbeat a foreign leader into doing something illicit that is providing dirt on his opponent during a presidential campaign, then that may be the only remedy that is coequal to the evil that conduct represents,” he said.

The UPI contributed to this report.