The Ministry of Business, Innovation and Employment is being accused of incorrectly recording figures for forestry deaths.
Council of Trade Unions president Helen Kelly says the ministry told the CTU that 23 forestry workers have died on the job since 2008.
But she says she learned of another worker not on that list when the widow of Shane Frater, who died in a job accident in 2009, approached the CTU about attending a memorial service planned for the dead workers.
Ms Kelly says even though the ministry investigated his death, it has not been recorded on any list and they cannot find his file.
The ministry says Mr Frater's file is in the system but was wrongly coded, and thus not picked up.