Lambert is believed to have been shocked by the attitude and lack of professionalism amongst a few senior members of the squad when he arrived at the club in January.
"Listen, there was things going on that, if I let that away, my standing would drop," Lambert said.
“I was never going to have it. I'm too professional. I've been at big clubs myself, know how the game works, and that was unacceptable, what was going on. Massively unacceptable. My God, I've not seen anything like that."
Lambert said he had no regrets about his hard-line stance.
“Absolutely not. I'd have done it again. Because it was wrong. And if I'd never done it, I think the good guys at the club would have felt they didn't have much help. And anyone knows me knows that I'm fair, but my standards are high. But it is what it is. There's a core of good guys, the ones that have with me for the last few weeks or so."