MEXICO CITY (Xinhua) -- Mexican President Felipe Calderon called on all Mexico's political parties to bridge their gaps through consensus building to improve democracy.

All the political parties should make efforts to reach an agreement "without rancor and without repeating the errors and misunderstandings of the past," said the president at a ceremony on commemorating the 90th anniversary of the 1917 Mexican constitution and the 150th anniversary of the 1857 constitution.

Calderon, of the National Action Party, beat leftist candidate Andres Manuel Lopez Obrador in the presidential election with a slim margin last year. He took office for a six-year term on Dec. 1, 2006.

But Lopez Obrador refused to concede defeat, alleging massive fraud in the electoral process. His party has since kept organizing demonstrations against Calderon's rule.