Lennon, who left Bolton Wanderers in March after 17 months as manager, told BBC Sport: "It's high time that it's been exposed. People are taking money out of the game and it leaves a really bitter taste.
"You hear whispers from players and managers and agents. There have been rumours for a long, long time about other people. High-profile people. It's these unlicensed agents that are making money through third-party ownership, doing deals with cash involved and giving the game a bad name.
"In my time at Celtic, I spoke to agents, but when it came to negotiations, I left that to other people and I've done the same thing at both my other clubs.
"I'm not aware of any issues in Scotland and I've been up here for a long time. I'm not sure clubs could afford to pay extra money to these shadowy figures in the background."
The undercover investigation has also led to Barnsley assistant manager Tommy Wright losing his job at Oakwell, while other names implicated in the scandal include Queens Park Rangers boss Jimmy Floyd Hasselbaink and Southampton assistant manager Eric Black.