Leeds manager Marcelo Bielsa admitted he was responsible after a club employee was caught spying on Derby's preparation for a Championship clash between the two sides on Friday.

Derby released a statement earlier on Friday saying police had been called to their training ground on Thursday to investigate an intruder "acting suspiciously".

Bielsa, who has enjoyed a storied career in charge of Argentina, Chile and a host of European clubs, claimed he had used the practice of spying on opposition's training sessions for nearly 20 years dating back to Argentina's qualifying campaign for the 2002 World Cup.

"It's true there was someone from Leeds United," the Argentine told Sky Sports. "The responsibility for this lies with me. I'm responsible.

"It doesn't matter if it's legal or illegal, or right or wrong. For me it's enough that Frank Lampard and Derby County feel it was not the right thing to do and that I didn't behave well.

"I didn't ask permission from Leeds United to do it so it's my responsibility.

"Without trying to find a justification, I've been using this kind of practice since the qualifications for the World Cup with Argentina."

Former England and Chelsea midfielder Lampard is now in charge of Derby and believes no matter the cultural differences, Bielsa's actions were unsportsmanlike.

"At least, on a sportsman's level, it's bad in my opinion," said Lampard.

"If we're going to start talking about 'culturally, I did it somewhere else' - that doesn't work for me.

"If I'm lucky enough to do well and travel to another country I'll find out what the etiquette is in that country and abide by that.

"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."

Leeds are top of the Championship and in line for a return to the Premier League after a 15-year absence, but have lost their last three games.

Derby occupy the final playoff place in sixth but can close to within three points of automatic promotion with a win at Elland Road.