The miners requested pay parity, which Solid Energy claimed could amount to wage increases of up to 30%. Solid Energy had offered a 2.8% general wage increase, plus continued access to profit sharing, at talks with the Engineers Union on Monday April 18.

Solid Energy estimated 500 employees and contractors had stopped work in support of current collective agreement negotiations covering Rotowaro opencast, Huntly underground, Stockton opencast, Spring Creek underground, Strongman opencast and Ohai opencast mines, along with the Ngakawau coal handling facility.

Solid Energy said the industrial action would cost the company about $NZ1.5 million a day in lost production.

Solid Energy chief operating officer Barry Bragg said that the action would cause significant disruption to the operations of its New Zealand customers, as well as the company’s transport operators, as the union had given no formal notice of the industrial action.

The union said it wanted a national, multi-employer agreement to ``counter Solid Energy's attempts to drive down wages by contracting out work''.