The Irish Congress of Trade Unions (ICTU) says a new protocol that will see people return to work is not discretionary.
It says every employer "has an absolute duty to adhere to the rules" which are being put in place.
The protocol includes information for employers and workers relating to social distancing, hand hygiene, first aid and mental health.
It also covers issues such as ventilation and heating to reduce the risk of COVID-19 in the workplace.
The Return to Work Safely Protocol is the result of intense discussions involving ICTU, employers, the Health and Safety Authority (HSA), the Health Services Executive (HSE) and the Department of Health.
ICTU General-Secretary Patricia King was speaking ahead of the official launch of the document on Saturday.
She said the agreement is "an essential weapon in the war against a dangerous and insidious virus".
Ms King said: "The battle against COVID- 19 demands an unambiguous policy in relation to health and safety.
"We welcome the role which workers have been given in enforcing the protocol in the workplace".
She emphasised that the protocol was not discretionary and every employer has an absolute duty to adhere to the rules.
"It is vital that the protocol is supported by an effective, enforcement regime and that every employer and worker plays their part in making our workplaces safe for all".
She added: "The price of negligence is too high. There can be no shortcuts or opt-outs when it comes to matters of life and death.
"COVID-19 does not discriminate and every worker in every sector is entitled to the protection of this protocol."