“It’s disrupted our build-up to this game. People are going to say I’m trying to make an excuse – but I’m going to speak like this after the game win, lose or draw. How you prepare the team is vitally important and we haven’t been able to do that on Friday.
“I don’t think we need to [investigate], because he’s admitted it so it’s easily dealt with. It’s up to the league to see how they deal with it.
“Obviously it’s not just Derby County, we had somebody the day before our first game against them which we lost 4-1. Now Leeds can beat you 4-1, they’re a fantastic team, but we had somebody in the bushes that day, twice this season now.
Biesla’s behaviour is likely to have upset other Championship managers, as they will suspect their training sessions have also been spied on this season by the league leaders.
“It’s true there was someone from Leeds United,” said Biesla when asked about the incident. “The responsibility of this is me, I am responsible, there is some precision that I need to give.
“It doesn’t matter if this is legal, illegal, right or wrong, for me it’s enough that Frank Lampard and Derby County felt it was not the right thing to do. I didn’t behave well.