Paul Cavanagh was filmed outside a home in Gateshead to teach colleagues a new safety measure.
However, the demonstration went wrong when Cavanagh, who was tethered to the ladder, slid sideways and crashed into a neighbour's garden.
As he lay on the ground, one worker observed: "That proves the system doesn’t work then.”
Footage of the failed demonstration has been viewed nearly 200,000 times on YouTube.
Cavanagh is understood to have not been seriously hurt in the fall, but has been suspended for breaching safety protocol by not anchoring the ladder to the wall.
Chris Morgan, director of health and safety for Morrison FS posted a message on the YouTube site: "We are dismayed by this isolated event, resulting from an individual deciding not to comply with our stringent H&S standards.
"This has led to suspension, pending investigation. We strive to ensure that everyone gets home safely, every day and are proud to have one of the lowest accident rates in sector. Please be sure that we have responded appropriately to this incident and that we will always endeavour to operate to the highest safety standards."