Major public investment in new venues and convention centres may be doing more harm than good.

The Government has committed to a new Sky City convention centre in Auckland, and is on board to build a convention centre in Christchurch.

It claims the centres are critical to drawing more conferences to New Zealand.

But economist Dr Eric Crampton claims they are more likely to draw events away from smaller provincial centres.

"To that extent it can be OK for Christchurch but not so hot for the country as a whole," he said.

Crampton said the business case for convention centres often doesn't stack up..