(Inserts dropped word "some" in second paragraph)

MEXICO CITY, Jan 31 (Reuters) - Mexico's president on Tuesday sought to overturn rules the country's telecommunications agency imposed on broadcasting networks and limit the regulator's power.

President Enrique Pena Nieto filed a constitutional challenge in the Supreme Court that argues the agency does not have the authority to regulate some broadcast content, Humberto Castillejos, his chief legal counsel, told a news conference.

The regulation on so-called audience rights, published in December by the Federal Telecommunications Institute (IFT), set out rules applying principally to Mexico's largest broadcaster Televisa and its rival TV Azteca.

Audience rights is a term in Mexican law that encompasses issues such as advertising disguised as journalism, the line between opinion and fact and discriminatory content.

Castillejos argued audience rights were part of the human right to information and should fall under the executive branch's authority. The suit challenges eight articles of a 2014 telecoms and broadcasting sector law largely written by Pena Nieto's government.

"It's going against its own law," said Aleida Calleja, a telecoms analyst with information rights think tank AMEDI. "They are taking audience regulations as a pretext to try to undermine the autonomy of the regulator."

The IFT published the regulatory guidelines on Dec. 21 in the government's official gazette. They are due to come into force in February.

A spokesman for Televisa did not immediately respond to a request for comment.

The IFT said in a statement that its regulations complied with the law.

(Reporting by Christine Murray; Additional reporting by Lizbeth Diaz; Editing by Cynthia Osterman)