Democrats on the House Oversight and Judiciary Committees are asking the Justice Department’s inspector general to investigate whether Attorney General Jeff Sessions violated his recusal when he recommended the firing of former FBI Director James Comey.

Sessions, who was a top surrogate in Donald Trump’s presidential campaign, has recused himself from the investigation into Russia’s meddling in the presidential election, which is looking into possible coordination between Russia and the Trump campaign.

But in congressional testimony earlier this month, Sessions defended his decision to recommend Comey’s firing, saying the Russia probe was just one of many investigations being overseen by Comey.

“The actions of Attorney General Sessions in collaborating directly with President Trump to fire Director Comey reflect a lapse in judgment by our nation’s top law enforcement official and appear to violate multiple promises made by the Attorney General and his aides,” all the Democrats on the Oversight and Judiciary panels said Thursday in a letter to the Justice Department’s inspector general.