Read More Netflix CEO slams Comcast's bid for TWC
Among the "significant" potential harms that DISH identified in the merger are "discriminatory data caps," and "restriction of third-party online rights" stemming from the large market share of a successfully merged company.
"Here, the public interest benefits [Comcast and Time Warner Cable] claim are unlikely and speculative. Further, the claimed benefits do not come close to outweighing the anti-competitive effects of the transaction, and the serious damage that will be inflicted on consumers if the merger is approved," the company said in its petition.
For its part, Comcast has repeatedly argued that a merger with Time Warner Cable would spur industry innovation rather than stifle it.
Disclosure: Comcast is the owner of NBCUniversal, the parent company of CNBC and CNBC.com.