Genesis has labelled Meridian's statements regarding prompt payment discounts ''unhelpful'', in a sign of intense pressure felt by power companies facing a pricing review and locked in a heated battle for customers.
Genesis chief executive Marc England said the best way to help vulnerable customers - one focus of the review of the electricity sector - could be a collaborative industry approach.
''Collectively, we need to put help where help is needed most at the same time as we allow genuine and sustainable competition to deliver benefits of choice and innovation to consumers,'' England said.
Meridian says it is taking away prompt payment discounts but also eliminating penalties for about 8000 of its customers who were penalised for paying their bills late.
The company's chief executive Neal Barclay has said the outdated system was one of the industry's ''dirty secrets'' and needed to go.