The crusading host of Mexico's top-rated national news radio program has been fired in a case that many fear is a blow to freedom of expression.

MVS Radio says Carmen Aristegui was fired for challenging the firing of reporters who had misused the company's name by linking it to a website meant to collect leaks of government information.

But defenders of Aristegui note that the firing comes a few months after the same reporters had embarrassed President Enrique Pena Nieto by revealing his wife had a house financed by a frequent government contractor.