Christchurch City Council is defending an ultimatum to commercial property owners to either fix earthquake damage by 31 January, or pay for the council to do the work itself.
Notices have been sent to owners of some buildings damaged by the magnitude 7.1 earthquake on 4 September.
The Property Council says it will add to the stress on owners.
But enforcement manager Gary Lennan says notices have been sent only to owners who have not told the council what their plans are.
Mr Lennan says the deadline may be extended if there is a reasonable explanation for the lack of progress on repairs.
He says 500 damaged commercial buildings are being monitored.
Mayor Bob Parker says the city council is not being heavy-handed.
He told Morning Report the council's first responsibility is to protect people's safety.