(Adds context on the bill)
MEXICO CITY, July 3 (Reuters) - Mexican Senate committees on Thursday gave their general approval to legislation needed to implement a reform of the phone and TV markets that seeks to rein in telecoms tycoon Carlos Slim and broadcaster Televisa.
Reservations raised by the committees over the so-called secondary laws will be debated on the floor of Senate, which is expected to put the legislation to a full vote on Friday.
Lawmakers from the ruling Institutional Revolutionary Party have said they expect the legislation, which has been delayed for more than six months, to pass to the lower house for final approval next week.
President Enrique Pena Nieto's reform last September created a new regulator, the Federal Institute of Telecommunications (IFT), which declared Carlos Slim's America Movil and broadcaster Televisa dominant on the basis of their market share, subjecting them to tougher regulation.
America Movil controls about 70 percent of Mexico's mobile market and 80 percent of the fixed line business. Televisa, the world's biggest provider of Spanish-language content, has over 60 percent of the free-to-air TV market.
However, because of the legislative delay, the regulations setting out the IFT's precise remit have not yet been finalized. Any changes made to the secondary laws could interfere with its faculties.
Critics of the proposed legislation said lawmakers aligned with Televisa in particular are trying to make dominance dependent on a firm's market share in the whole of the telecoms or broadcasting sector rather than particular services, such as pay TV.
That, they say, could make it easier for companies to evade tougher regulation. Both America Movil and Televisa have used legal maneuvers to beat back efforts to regulate them in the past, though the reform reduces their ability to do so. (Reporting by Christine Murray and Dave Graham; Editing by Miral Fahmy)