Civil defence authorities had difficulty organising volunteers after the Christchurch earthquake because there were so many of them, the government says.

A forum has been held to discuss the problems and Civil Defence Minister Chris Tremain says changes will be made.

"The extent of spontaneous volunteering was a new phenomenon that Civil Defence Emergency Management (CDEM) had not previously experienced," he said on Tuesday.

"Many volunteer organisations expressed frustration that structures were not flexible enough to channel the skills and energy being offered."

Mr Tremain says one solution is the appointment of volunteer co-ordinators within CDEM.

They would identify the volunteer groups during the early stages of a response and direct them to specific tasks.

"I'm confident these lessons will be reflected over time, with CDEM changing the way it works with spontaneous volunteer groups," he said.