WASHINGTON ― The top congressional watchdog in the House must dig into allegations around President Donald Trump’s national security adviser Michael Flynn ― or step aside ― Democrats demanded Monday.

Flynn is embroiled in a scandal over his reported contacts with Russians, and discussions with the Russian ambassador about sanctions that he allegedly had before Trump’s inauguration. Flynn at first denied the talks, then said it was only one conversation, then said he could not remember what he talked about. He resigned late Monday night.

Democrats have repeatedly called on Congress to launch probes into Russia’s attempts to influence the 2016 election against Hillary Clinton, with limited success. Democrats on the House Committee on Oversight and Government Reform, chaired by Rep. Jason Chaffetz (R-Utah), had already asked Chaffetz to seek various documents from the FBI, National Security Council and Department of Defense regarding Flynn’s vetting for his job.

Chaffetz has declined to do so.

The new revelations about Flynn’s reported Russian contacts, which prompted conflicting responses from White House advisers Monday, spurred Democrats to express greater alarm.

“Today, all Democratic Members of the Committee write to you jointly to request that you either reconsider your decision and initiate this investigation, or step aside and allow the Committee to vote on conducting basic oversight going forward,” the Democrats wrote in a letter to Chaffetz, noting they’ve been seeking Flynn-related probes since August.

Chaffetz’ office did not immediately respond to a request for comment from The Huffington Post. Chaffetz told reporters outside a GOP meeting Tuesday morning that he was not interested in investigating Flynn.

Rep Jason Chaffetz R-UT tells reporters there's no need to further probe Flynn. "It’s taking care of itself" — Jamie Dupree (@jamiedupree) February 14, 2017

Democrats find the reluctance of Chaffetz to investigate the Trump administration and the alarming reports about Flynn especially frustrating after Republicans focused so doggedly on Clinton’s role in Benghazi and her ill-considered private email system.

“It is difficult to imagine a more serious list of allegations for our Committee to investigate,” the letter said. “They demand a robust, immediate, and bipartisan investigation rather than partisan stonewalling and the transparent excuses for inaction. If you are not willing to take action, then we ask that you allow us to do our job by scheduling a vote on proposals from other Members of the Committee.”

This post has been updated with Flynn’s resignation and a Tuesday comment from Chaffetz.