More then 700 volunteers are giving up time today to help Auckland City Mission on its biggest day of the year.

300kg of ham, 240kg of chicken and 400 litres of ice cream will be dished up today at the mission's annual Christmas lunch.

City Missioner Dianne Robertson says only 2000 people can be accommodated, but she's promising to help as many as possible.

"We've stopped giving out tickets after a certain period of time, but we don't turn anybody away hungry."

Robertson says most of the hard work is already done.

And there are 700 volunteers on hand to tackle the rest.

"The pre-cook is done, we've got everything down at the Events Centre and it really is all just sitting there waiting."

Christchurch City Mission also has a big day planned, with work starting this morning on a lunch for 600 guests.

There's lamb, pavlova and mince pies on the menu.

City Missioner Michael Gorman says the event can be a saving grace for people who are struggling.

"They really look forward not just to the meal but being together, catching up with old friends.

"And then jolly old Santa Claus comes and he has gifts for the children as well."