The European Commission has accused Altice of breaching EU rules by taking over Portugal Telecom before the deal was formally approved.
Altice could face a fine of up to 10 percent of its annual turnover if the Commission was to conclude it was in breach of rules.
The French telco notified the Commission of its intention to take over the Portuguese operator in February 2015. While the Commission cleared the transaction two months later, it was subject to certain conditions that centred on Altice's divestment of its Portuguese subsidiaries Cabovisão and ONI.
Yesterday the Commission issued a Statement of Objections, outlining its concerns. Altice can reply in writig or request an oral hearing to defend their case to Commission representatives and competition authorities.
Commissioner Margrethe Vestager, who is responsible for competition policy, said: "If companies jump the gun by implementing mergers prior to notification or clearance, they undermine the effective functioning of the EU merger control system.
"The Statement of Objections sent to Altice shows how seriously the Commission takes breaches of the rules designed to protect the merger control system."
In a statement responding to the European Commission, an Altice spokesperson said: " Altice does not agree with the European Commission’s preliminary conclusions, and will submit a full response to the statement of objections and contest all the objections. The sending of a statement of objections does not prejudge the final outcome of the investigation."
French regulator Arcep fined Altice €80 million for jumping the gun on acquiring SFR and Virgin Media last November.