MEXICO CITY -- A radio station broadcast what it described as a telephone conversation in which a federal lawmaker and one of Mexico's biggest drug lords express support for each other.

W Radio said the alleged conversation took place last year between lawmaker Cesar Godoy Toscano and La Familia cartel leader Servando Gomez, known as "La Tuta." In it, Godoy and Gomez express support for each other and discuss bribing a reporter.

Godoy represents the western state of Michoacan, La Familia's stronghold. He already faces federal charges for allegedly protecting the cartel but has immunity from arrest because he is a congressman.

He was one of 36 people in Michoacan -- including politicians, mayors, prosecutors, police and judges -- accused last year of ties to La Familia, known for beheading rivals and bold attacks on soldiers and police.

W Radio said the conversation was included among evidence federal prosecutors sent to Congress in a petition to have Godoy's immunity lifted. The station did not say how it obtained the recording.

Officials at the Attorney General's Office refused to confirm or deny the authenticity of the recording.

The press office at Mexico's lower house of congress said Godoy would not comment. The lawmaker, of the leftist Democratic Revolution Party, or PRD, has previously proclaimed his innocence.

In the recording, a man identified by W Radio as Gomez expresses support for Godoy and certainty that he will win the election.

"Buddy, first of all I want you to win. ... You can count on full support, you are going to win," the voice says.

The conversation also mentions an unidentified Mexican reporter in the pay of La Familia. The man identified as Godoy expresses his annoyance that the reporter published articles critical of his party and asks Gomez to do something about it.

Godoy -- half brother of Michoacan Gov. Leonel Godoy -- was the only one of the 36 suspects who escaped arrest in the sweep last year.

At the time a candidate for congress, Godoy fled and continued his campaign from hiding. Despite the charges against him, he won his congressional seat in July 2009 elections.

Godoy remained in hiding for more than a year until he unexpectedly showed up at Congress last month and was sworn in after evading police officers who had surrounded the building to arrest him. Federal prosecutors are legally barred from arresting him have but filed a petition to have his immunity lifted, which could require a congressional vote.

PRD Secretary-General Hortensia Aragon said that if the recorded telephone call is legitimate, Godoy Toscano should step down as legislator temporarily so he can face justice.

"If the case, as presented today, is true, (Godoy Toscano) should request a leave of absence and legally defend himself like any other citizen," Aragon said.

The Michoacan corruption investigation has largely unraveled and turned into an embarrassment for the government of President Felipe Calderon, which has sought to demonstrate that no politician is immune in the fight to destroy drug trafficking cartels.

One by one the mayors and other officials arrested have been freed for lack of evidence, and today only one suspect, a mayor, remains behind bars.

Their release has fueled accusations that the sweep was a political ploy to gain support ahead of the July 2009 vote, in which Calderon's National Action Party suffered significant losses amid a flagging economy and rampant drug gang violence.

The government denies the sweep was politically motivated, noting that some of the mayors arrested were from Calderon's party. Federal prosecutors have filed a complaint against the judge who ordered the officials released and they insist the investigation against all 36 suspects continues.

Prosecutors have refused to discuss the evidence against any of the officials, and the