As federal antitrust regulators review Comcast Corp.’s pending $45 billion purchase of Time Warner Cable Inc. and AT&T Inc.’s $49 billion deal for DirecTV LLC, competitors and public interest advocates are on the attack — and they’re lawyering up with outside and in-house counsel to fight.

Filings with the Federal Com­mun­i­ca­tions Commission (FCC) show that at least a dozen companies or groups including Dish Network Corp., Netflix Inc., Cogent Communications Group Inc. and the American Cable Association have hired outside counsel including Boies, Schiller & Flexner and Steptoe & Johnson LLP to lobby regulators during the merger review process. Others like Free Press, Broadview Networks Inc. and the Independent Telephone and Telecommunications Alliance are handling advocacy in-house.