Fiji's Minister of Labour, Kenneth Zinck, says the unions knew about the penalties that would be included in the new Employment Relations bills, and had agreed to them.
And, he says they will remain in the bill which is due to be presented in parliament next week.
Mr Zinck says the unions have had the last two years to comment on the bill after widespread consultation, and it's too late to change it now.
The trade union movement has said it would take action if the stiff new fines of up to 30,000 US dollars remained in the bill.
Mr Zinck says any union covering essential services, whose members take part in a strike deemed to be illegal, could face the fines if all else fails.
"The essence of the bill is bargaining in good faith and also speedy resolution of disputes and it ends up with the Labour court. It's really the Labour court that will impose those fines. It's not the ministry. Once it goes to the Labour court, it's out of our hands so it's really the empowerment of the Labour court to charge them or make those fines."
Mr Zinck says heavy fines will also apply to employers who are found not to be paying fair wages or other terms and conditions.