The CTU's head says excessive dividends for shareholders are stopping power companies investing more in generation. 

The union says the partially Government-owned gentailers should re-nationalise. 

Energy Minister Simon Watts will make an announcement tomorrow on sector reform. 

Richard Wagstaff says gentailers have their priorities wrong. 

"Between 2016 and 2020, there's 1.2 billion in capital expenditure - that was about a fifth of the dividend payout. There's no more generated today than there was 10 years ago."

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