In a speech to Tories at grassroots level, the Conservative leader said that, while there was often a "noble" intention behind health and safety rules, Labour had an "over-the-top" culture of health and safety.
But the TUC's general secretary, Brendan Barber, said: "The idea that employers are being over-zealous in their application of health and safety regulation is simply not true.
"The reality is exactly the opposite - last year 246,000 people were injured at work. Neither does the UK have an excess of regulation - there were more than twice as many health and safety regulations and laws 35 years ago as there are now. Today's safety laws are generally simpler and easier to understand."
Since the passing of the Health and Safety at Work Act (1974), the UK has seen disasters such as the Piper Alpha oilrig and the Morecambe Bay cockle pickers. And, according to the TUC, occupational cancers still kill between 10 and 20,000 people every year and around 1.2 million people suffer from ill health at work.
Barber added: "Health risks need to be identified and dealt with so that workers and the public are protected. While some organisations use health and safety as an excuse not to do something, and others misinterpret the law, the Health and Safety Executive has tirelessly campaigned to ensure that employers address the real risks at work, rather than concentrate on the trivial."
Andrew New, product development manager at St John Ambulance, said: "Let's be clear that first aid is a vital part of health and safety. Underlying this whole debate is our attitude towards first aid.
"In the UK, first aid is often seen as fulfilling a legislative requirement rather than being a necessary skill that saves lives. If more people were trained in first aid this would make a tremendous contribution to reassuring event organisers, businesses and the UK public that help was at hand to deal with everyday accidents - maybe they would be less inclined to over-react to regulations if they had that confidence."
"As it stands at the moment, there is a great deal of confusion about the regulations and all of us working in health and safety need to do more to make clear how they should be interpreted. Organisations want to do the right thing, but don't always know how. Somehow common sense gets lost, and we end up with the stories we all see about health and safety gone mad.
"Cameron has certainly opened an interesting debate and we look forward to seeing the results of Lord Young's work in this area."