Millions of workers will face a greater risk of accidents or injuries if the UK leaves the European Union, the TUC is warning.
Legislation from Europe has helped stop illnesses and injuries in the workplace and has saved lives, according to the union organisation.
A study found that almost two-thirds of British health and safety regulations introduced between 1997 and 2009 originated from Europe, helping to reduce workplace fatalities.
Construction workers and police officers are among those to benefit, while protections against asbestos have been strengthened, said the TUC.
If the UK votes to leave the EU, the Government would be able to decide whether to keep protections derived from EU laws, according to the report.
TUC general secretary Frances O'Grady said: "On International Workers' Memorial Day 2016, it's clear that voting to leave the EU is a big risk for people's safety at work.
"Brexit could see many of the vital protections that keep workers safe in shops, factories, offices or on building sites stripped away, leaving millions of people at increased risk of accident or injury in the workplace.
"The Government has already hinted its readiness to water down key health and safety rules should Britain vote Leave in June.
"We know that some of the biggest cheerleaders for Brexit see protections for ordinary British workers - like health and safety law - as just red tape to be binned."