Senator Ed Markey (D-MA) told Elon Musk, “Fix your companies. Or Congress will,” after Musk snarkily replied to the senator’s concerns about fake verified accounts on Twitter, and suggested Markey’s real account “sounds like a parody.”

On Friday, Markey sent out a tweet containing a link to a letter he wrote to Musk, criticizing the new $7.99 per month Blue with verification subscription. The letter cites a report from the Washington Post that details how a reporter was able to easily create a fake verified account impersonating Markey and calls on Musk to address the issue. “Twitter must explain how this happened and how to prevent it from happening again,” Markey writes.

Musk’s response? “Perhaps it is because your real account sounds like a parody.” The billionaire followed up with another tweet about an hour later, saying “And why does your pp have a mask?” in reference to the Senator’s profile picture on Twitter that shows him wearing a face covering.

Markey didn’t take too kindly to Musk’s reply and warned that Congress could take action against Musk and his many companies if he doesn’t straighten things out. “One of your companies is under an FTC consent decree. Auto safety watchdog NHTSA is investigating another for killing people. And you’re spending your time picking fights online,” Markey writes. “Fix your companies. Or Congress will.”

While Markey obviously doesn’t represent all of Congress, the Democrats will keep their control of the Senate following the midterm elections. Markey is also on a number of committees that could affect the Musk-owned Tesla — including the Commerce, Science and Transportation Committee — and has raised concerns over the electric vehicle maker’s full-self driving software several times in the past.