The builder brought the device onto the 2012 site in the cab of his digger just hours before the main Olympic Stadium held its first official event yesterday.
The worker told The Sun that he passed through checkpoints unchallenged with the bomb on board.
The paper had given the builder the dummy package to test security after he contacted them expressing fears over security levels at the site where £1bn has been spent protecting the games.
The builder said: “I’ve worked for several years on the Olympic Park and keep hearing how the security is water-tight.
“But after a thorough check every morning, I can come and go from the Park all the day with my digger without being searched at all.
“I can meet anyone on the outside without anyone knowing and bring anything inside without anyone checking. If I had terrorist connections I could be bringing in explosives, chemicals — anything at all.
“It’s a massive security loophole.”
Olympic organisers LOCOG said: “Clearly a tupperware box containing batteries, a mobile phone and some loose wires would not pose a security threat on a construction site.
“However, we will be looking into the allegations to ensure our security regimes are as robust as they need to be at this time.
“As you would expect our security increases significantly the closer we get to the Games. The Park and the Village will be searched and sealed before it is locked down for Games time.”
For a video of the security breach click here