UPDATED 3.32pm: Labour's Christchurch housing spokesperson wants the government to start taking its targets for the city's rebuild seriously.

It follows concern that National won't meet its promise to build 700 new social houses by December.

Paula Bennett was in Christchurch yesterday, opening two new social housing units in Linwood.

So far Housing New Zealand's only completed 200 of the 700 units promised this year, forcing the Minister to admit some could spill into next year.

Paula Bennett said the possible extension's not a concern.

"If it is we're talking months, certainly not years, and we're talking a few houses," claimed Bennett. "Technically we may go slightly over, but it's absolutely nothing to be alarmed about of where we are in the rebuild."

But Labour's housing spokesperson Poto Williams argues Social Housing Minister Paula Bennett is too blasé about whether the government will make that deadline or not.

"What [this] is saying is that this government doesn't meet its target, and actually it sets these unrealistic expectations for all of us in the community."

Housing New Zealand has so far repaired more than 4000 quake damaged properties, and aims to repair 5000 by the end of this year.