Labour has accused National of admitting DHBs will end up paying more for food supplied by Compass if they don't sign up with the private contractor.

Labour's health spokesperson, Annette King, says Health Minister Jonathan Coleman is worried about reports of growing discontent with the service.

The Southern DHB has faced a long-standing revolt about the quality of their Compass-supplied hospital food.

Current Compass food prices depend on all 20 District Health Boards signing up, but fewer than half have done so.