Andrés Manuel López Obrador, Mexico’s defeated leftwing candidate, pushed his civil resistance movement into increasingly radical territory on Monday after he proclaimed himself the country’s “legitimate” president and lashed out at political opponents.

Following a ceremony adorned with many of the trappings of a genuine presidential inauguration, Mr López Obrador, who narrowly lost the presidential election in July to Felipe Calderón of the centre-right National Action Party (PAN), said he would honour the country’s constitution and protect the rights of Mexicans.