Ucatt said the Health and Safety Executive's (HSE) research on the build phase of the Games "ignored the key safety factor".
The HSE study made a link between strong leadership and worker involvement and a safer working environment.
It said it had received reports of only 114 injuries and eight dangerous occurrences that occurred during the 66 million hours of work, as of October 2011.
But Ucatt said the safer working environment was down to only directly employed workers being employed on the Olympic Park.
The union said that by ensuring regularised employment and basic employment rights, workers had the confidence to raise safety concerns without the fear of being sacked.
It claimed accident rates on construction of the Olympic Village – where no such rules were in place – were consistently higher than the Olympic Park.
George Guy, acting general secretary of Ucatt, said: "It is vital to understand why the Olympic Park achieved a very low accident rate.
"If the construction industry really wants to learn the lessons from the Olympics it is that sites where workers are directly employed are far safer, especially when this is combined with strong union involvement from an early stage."
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