Washington (CNN) A coalition of Inspectors General is urging the Justice Department's Office of Legal Counsel to withdraw or modify its opinion that the whistleblower complaint regarding President Donald Trump's communications with Ukraine was not of "urgent concern," a determination that initially blocked the allegations from reaching Congress.

In a new letter sent to Assistant Attorney General Steven Engel this week, the Council of the Inspectors General on Integrity and Efficiency, which is composed of federal government inspectors general, slammed an OLC memo that "effectively overruled the determination by the ICIG regarding an 'urgent concern' complaint" that the ICIG concluded was "credible and therefore needed to be transmitted to Congress."

"This letter from the Council of the Inspectors General on Integrity and Efficiency, on behalf of the undersigned federal Inspectors General (IG), expresses our support for the position advanced by the ICIG and our concern that the OLC opinion, if not withdrawn or modified, could seriously undermine the critical role whistleblowers play in coming forward to report waste, fraud, abuse, and misconduct across the federal government," it states.

The letter, which was posted publicly and distributed to the media by DOJ OIG, amounts to a sharp rebuke of the OLC opinion and sign of solidarity from the officials who act as independent watchdogs of government agencies. CIGIE chairman, Michael Horowitz, is also the DOJ IG.

In strong language, the inspectors general elevated a disagreement over an interpretation of federal whistleblower law that was at the center of the early moments of the scandal around the President's call with the leader of Ukraine, which is now the subject of an impeachment inquiry in the House of Representatives.

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