Mexican lawmakers said they would formally complain to the attorney general's office Tuesday after finding hidden microphones believed to have been used to spy on the lower house of Congress.
The listening devices were found "in quite a lot of offices, listening to and checking the activities of lawmakers," said Armando Rios Piter, president of the house's political coordination committee, on Televisa channel.
It was unclear who was responsible but lawmakers would release further information when possible, a statement from the lower chamber said.
News reports said listening equipment was found in offices of the three main political parties and transcriptions of telephone conversations were also found. Officials from all three parties denounced the discovery of the spy equipment.
The wiretaps against politicians and legislators is an old phenomenon that demonstrates the "outdated system" and the need for reform in this area, said José Luis Jaime Correa, the deputy coordinator of the Party of the Democratic Revolution (PRD) in the Chamber of Deputies, according to Univision.
"It could have very severe implications if it is found that these practices were ordered from a federal government office or even foreign interests," he added.
The Internet had also been hacked across the chamber, according to La Jornada daily.
The discovery of the listening equipment comes as Mexico is the midst of its presidential race. There is widespread disappointment from the Mexican public for President Felipe Calderón and his National Action Party (PAN) due to the soaring levels of violence related to the drug war.
Mexico's Institutional Revolutionary Party (PRI), the country's once dominant party, is looking to regain the presidency after 12 years of opposition control. However after holding double the approval ratings of any other candidate going into December, the parties candidate, Enrique Peña Nieto, has slipped in the polls after a number of campaign blunders.