Seven Democratic senators have called for an investigation into Mr Hawley and Ted Cruz in the wake of the deadly Capitol riot that left five people dead.
Both senators have faced widespread criticism amidst calls for them to resign for their role in trying to challenge Joe Biden’s election victory.
Mr Hawley in turn filed his own counter-claim against the group of Democrats, in which he accused the lawmakers of submitting their complaint “in potential coordination with a campaign by partisan and dark-money groups that have peddled falsehoods about me and my objection.”
Mr Hawley and Mr Cruz have been accused of helping provoke the violence with their refusal to accept Mr Biden’s legal victory over Donald Trump, and Mr Hawley was photographed giving a clench-fisted salute to the rioters.
Mr Hawley’s own complaint is aimed at Sheldon Whitehouse, Richard Blumenthal, Sherrod Brown, Mazie Hirono, Tim Kaine, Tina Smith and Ron Wyden.
In the complaint he demanded to know what contact the senators had with the Lincoln Project “or any other outside organisation.”
The Lincoln Project was started by a number of communication-savvy anti-Trump Republicans, including Steve Schmidt, who has worked on the campaigns of former President George W Bush, former California Governor Arnold Schwarzenegger, and former Arizona Senator John McCain.
Democratic senators had collectively written to the ethics committee last week demanding an investigation of Mr Hawley and Mr Cruz.
“In light of the shameful abuse of the ethics process you have deliberately engaged in, I have considered whether I should call for you to resign or be expelled from the Senate,” wrote Mr Hawley to the Democrats.
“But I continue to believe in the First Amendment, which the US Supreme Court has repeatedly said protects even ‘offensive’ and malicious speech, such as yours."
The Lincoln Project has targeted Mr Hawley for his actions earlier this month and have labelled him “complicit” for his attempts to support Donald Trump’s lies about election fraud.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies