The Irish Congress of Trade Unions says employers are responsible for the delivery of essential services and they must provide safe workplaces.
A list of 16 essential service sectors was published by the Government yesterday.
These include Agriculture and Fishing, Electricity, Gas and Water, Information and Communications and construction projects relevant to the COVID-19 crisis.
There is also a list of essential retailers that are allowed to continue operating, which is available here.
Members of the public have been ordered not to leave their homes except in limited circumstances, such as shopping for essential items, picking up medicines, attending medical appointments and exercising within 2km of their homes.
People are only permitted to go to work if the service they provide is considered essential.
The lockdown, aimed at containing the spread of COVID-19, will remain in place until Easter Sunday at the earliest.
ICTU General Secretary, Patricia King, says those who are allowed to go to work during the coronavirus crisis must be protected.
She said: "You may very well have workplaces that are close, and the employers are going to have to invest in what is required to ensure that the workplaces are safe.
"It would be completely unacceptable that workers are required to go to work and feel unsafe.
She added: "It is important that they know there is a piece of legislation there to protect them and it's important that the employer does not cut corners."
Additional reporting by Michael Stains
