The Council of Trade Unions believes the fine handed down to a company for failing to ensure the safety of its workers at Pike River should have been higher.
Valley Longwall International has been fined $46,800.
The Australian based drilling company had pleaded guilty to three charges of failing to ensure inspections and checks were carried out on its equipment.
Secretary Peter Conway says the maximum fine for each charge could have been $250,000.
"$46,000 is a very low fine. Three people lost their lives, and as the judge said, you can't abdicate responsibility and pass it on to someone else. So this firm has to accept a high level of responsibility for what happened.
Valley Longwall International says it accepts the fine.