School cleaners, caretakers, canteen and groundskeeping staff, hospital catering workers, orderlies, and cleaners - among others - could be paid New Zealand's living wage of $29.90 if the left bloc gets elected.

Labour's Chris Hipkins has signed a pledge to support this proposed policy, alongside Green co-leader Marama Davidson and Jessica Hammond from the Opportunity Party.

E tū Union director Finn O'Dwyer-Cunliffe says this could impact 20,000 workers across the country if implemented.

"It would not cost anything like some of the costs put into other areas - we already have contracted companies in catering, cleaning and security who employ people in Government departments who are paying the living wage and there's no reason it shouldn't be extended out."

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