MEXICO CITY, Dec 20 (Reuters) - America Movil, the telecoms giant controlled by the family of Mexican billionaire Carlos Slim, said on Thursday that it had been fined nearly $128 million by the country's telecoms regulator, a decision it vowed to fight.
In a notice to the Mexican stock exchange, America Movil said its Telmex subsidiary had been slapped with a fine of 2.54 billion pesos ($127.74 million) by Mexico's Federal Telecommunications Institute (IFT).
Telmex was penalized for allegedly failing to meet quality standards for the telecoms infrastructure it offered other companies in 2013 and 2014.
America Movil and Telmex said they would exercise all legal avenues in challenging the fines.
"This illegal and disproportionate fine affects the certainty and legal security in a sector that requires important investments for its development," the companies said in the statement.
A spokesman for America Movil and a spokeswoman for the telecoms regulator did not immediately respond to requests for comment.
America Movil, which was created from a state monopoly, is Mexico's largest telecoms operator by far.
The infrastructure of Telmex, its fixed-line subsidiary, is critical for smaller players such as AT&T and Telefonica , which use it to transmit calls and data.
In March, the telecoms regulator approved a plan to separate part of Telmex and Telnor, another fixed-line unit, into new companies. While America Movil has long been required to share its infrastructure, rivals have complained the access is insufficient. ($1 = 19.8845 Mexican pesos) (Reporting by Julia Love; Editing by Sunil Nair)