Marcelo Bielsa has accepted full responsibility for the Leeds United spying scandal but showed no remorse in a remarkable defence of his actions.
The Football Association (FA) is to investigate the incident after Derby County - ahead of Friday's Championship clash between the clubs - claimed a man caught by police acting "suspiciously" near their training ground was a Leeds employee.
Law enforcement personnel were called to Derby's training centre on Thursday after concerns about the behaviour of the individual outside the premises.
Police confirmed a man was found and questioned at the perimeter fence of the complex, before being sent on his way with no arrest made.
Media reports claimed the man involved was a "spy" sent by Leeds and Bielsa confirmed those allegations, revealing that he personally sent the man in question without notifying the club.
"It's true that there was someone from Leeds," Bielsa told Sky Sports. "The responsibility is with me.
"There are some decisions I need to give, it doesn't matter if it is legal or not. For me it is enough that Derby and [Rams boss] Frank [Lampard] felt it was not the right thing to do and that we didn't behave well.
"Yesterday I talked to Frank and, for him, he felt I didn't respect fair play rules. I have a different point of view on it.
"But the important thing is what Frank and Derby think of it.
"I'm the only person responsible for it because I didn't ask the permission of the club to do it.
"Without trying to find a justification, I've been using these practices since the qualifications for the World Cup with Argentina.
"This is not unlawful, we've been doing it publicly, we talk about it in the press. For some it's the wrong thing and for some it's not."
Thursday's discussion between the pair did little to placate Lampard, who struggled to hide his anger in his own pre-match interview with Sky.
The former Chelsea and England midfield also claimed Leeds sent a spy to Derby training before the sides met in August at Pride Park – a game United won 4-1.
"If we're going to start talking about 'culturally I did it somewhere else and it was fine', then that doesn't work for me because I don't believe it is fine on that level," Lampard said.
"It's disrupted our build-up to this game and the unfortunate thing for us is it disrupted us at our end without us doing anything.
"People are going to say I'm standing here trying to make an excuse pre-game – I will speak like this after the game and more if I have to, win lose or draw, because of what's happened.
"What I will say is we were training the day before the game on team tactics, team shape, personnel, how we're going to press, how we're going to work off the ball.
"If somebody wants to say that's not relevant and that won't affect a game… if tactics aren't relevant then Pep Guardiola, [Mauricio] Pochettino, Jurgen Klopp and all the great managers, they're just lucky."
Lampard added: "Obviously it's not just Derby County. We had somebody the day before our first game against them that we lost 4-1.
"Now, Leeds can beat you 4-1 – they're a fantastic team. But we had someone in the bushes that day. It's twice this season now.
"The man was asked to leave but it wasn't followed up like it was this time."
Leeds are top of the Championship table despite losing their past three games in all competitions, while Derby occupy the final play-off spot in sixth.