The mayor of Christchurch offered a formal apology on Sunday to families, including from Japan, who lost loved ones in the collapse of a six-story building in a 2011 earthquake.

Mayor Lianne Dalziel, who took office in 2013, met privately with the families in the central New Zealand city's Arts Centre to convey the apology.

Of the 185 people across the city who died in the magnitude 6.3 earthquake, 115 were in the Canterbury Television Building which crumbled to the ground in seconds, including 28 Japanese students attending an English-language school on the building's third floor.