Rally for Lopez Obrador in Mexico

Tens of thousands of people with flags and banners gathered in the Zocalo, the main square, to mark the anniversary.

Mr Lopez Obrador has never accepted his defeat by Felipe Calderon in the July 2006 presidential race.

Losing by less than one percentage point, he alleged electoral fraud and named himself "legitimate president".

His call for street protests paralysed Mexico City for weeks after the election.

Since then, the left-leaning politician has travelled around the country to continue his campaign.

'Won't be back'

Addressing the crowd, he reiterated his claim to the presidency and said that there should be "zero negotiation" with Mr Calderon.

But attendance at the demonstration was much smaller than those staged a year ago, and some Mexicans say he is becoming an increasingly irrelevant political figure.

"It is not the same; there are very few people," street sweeper Raul Coronel told Reuters news agency. "He lost and I don't think he will be back."

Mr Calderon's crackdown on the drugs trade has won him popularity and a recent poll showed his approval rating at 65%.

But Mr Obrador still has some supporters.

"The movement is not dead," supporter Jaime Taylor told the Associated Press news agency. "We only trust the legitimate government... and that is Lopez Obrador."