Businesses are taking class-action over a power outage to of all Northland last year - although the exact loss is still unknown.

In June, an inexperienced worker removed nuts from three legs of a pylon, which toppled, cutting electricity to almost the entire region.

An opt-out class action against Transpower and its lines maintenance contractor is progressing through the courts. 

Stout Street Chambers partner, Mike Colson, says losses will be calculated in due course. 

"It's giving Northland businesses an opportunity to be compensated - and second, an opportunity to incentivise those working on critical infrastructure to do a good job out of it." 

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• Two workers on collapsed Transpower pylon had ‘no formal training’
• 'Inconceivable' - bolts removed from pylon caused collapse, power outage
• 'Unacceptable': Energy Minister on fallen pylon that cut power for 100,000 Northlanders