The leftist opposition taunted President Miguel de la Madrid during his final state of the union address with chants of "Fraud! Fraud!" and walked out in a rare show of disrespect to the presidency.

The raucous heckling, which came Thursday as de la Madrid delivered his speech before a heavily guarded session of Congress, was unprecedented in modern Mexico, where the president has long been a symbol of national unity and off limits to harsh criticism.But disputed presidential elections in July have led the normally stoic Mexican public to fervently demand change from the government dominated by the Institutional Revolutionary Party, or PRI.

At a downtown rally of the conservative National Action Party, the party's presidential candidate in the July elections said Mexicans are tired of the nation's virtual one-party system and yearn for an end to authoritarian rule.

"The people booed most when de la Madrid referred to the `clean elections' because clearly this was untrue," said Manuel Clouthier.