Charter Communications Inc. urged Time Warner Cable Inc. investors not to endorse a takeover by Comcast Corp., setting up a battle for shareholder votes.

Comcast, which outbid Charter this year with a $45 billion stock offer, is too susceptible to regulatory hurdles because it’s the biggest in the cable industry, Charter said today in a filing. Time Warner Cable, meanwhile, refused to engage with Charter to develop a merger deal, Charter said.

The proxy filing shows Charter isn’t backing down in its pursuit of Time Warner Cable without a fight. Charter and Comcast have each pursued a takeover of the second-largest U.S. cable carrier to reduce costs and gain greater leverage in negotiations with networks like CBS Corp. and Viacom Inc.

Based on the value of its shares, Comcast’s merger offer was worth $158.82 a share when it was announced Feb. 13. That figure has fallen to $141.16 a share as of yesterday as Comcast shares have declined, Charter’s filing said.