Rangers boss Steven Gerrard believes Marcelo Bielsa was wrong to watch opposition training sessions and called for football's authorities to legislate against spying.
Bielsa on Wednesday admitted to having every one of Leeds' Championship opponents watched in training, while presenting his analysis of them to journalists.
Former Liverpool and England captain Gerrard said on Thursday: "I think Leeds have overstepped the mark in this case.
"It's not my way to send someone to other people's training grounds. There is not a law in place and until there is, it could happen again.
"The powers that be need to adapt the rules and get something in place for this kind of behaviour in my opinion."
The espionage admission came after a staff member of Leeds was caught by police at Derby's training ground attempting to gain information ahead of last Friday night's fixture, which Leeds subsequently won 2-0. The EFL and Football Association have opened investigations, with Bielsa saying he will cooperate.
Celtic manager Brendan Rodgers says it would be an exaggeration to call the Leeds head coach a cheat.
Former Swansea and Liverpool boss Rodgers claimed detailed knowledge of opposition can be garnered from leaks from players and their agents.
"I have seen 'cheating' being used but I think it's a bit strong," Rodgers said.
"In the current game there's probably more opportunity for teams to get out through agents and players within (clubs).
"Teams will always try to find an edge but there is so much analysis in the game, so much preparation that goes in from coaches and managers, that it would be very surprising if you didn't know the team or have a good idea of what the team was going to play.
"Marcelo Bielsa is an outstanding coach, someone I have admired for a long, long time.
"His methods, his way, are well documented in how successful he has been, he has explained his side of it and it moves on."
💬 | Marcelo Bielsa: "What I have done is not illegal. We can discuss it, it's not seen as a good thing, but it's not a violation of the law. I know that not everything that is legal is right to do." — Leeds United (@LUFC) January 16, 2019
Swansea boss Graham Potter, whose side drew 2-2 with Leeds in August and next face them in February at Elland Road, was unfazed by the episode.
Potter said: "I have no problem with it. If somebody has the resources and wants to get in a car and watch us train it's not something I'm too bothered about.
"I think the percentage of increasing your chances of winning by doing that are very, very small.
"When you are looking at analysis you are talking about the past, but then you still have 22 players on the pitch who have to make decisions and that's important what happens in the game."
Southampton manager Ralph Hasenhuttl does not think the level of detail Bielsa revealed in his analysis is anything remarkable.
Hasenhuttl, whose side lost to Frank Lampard's Derby in an FA Cup third round replay on Wednesday night, said at a media conference on Thursday: "Maybe the people outside don't know how managers are working, but now they know it. But I have to tell you, it is nothing new.
"Every manager in every league in Europe, I think, does it in that way."
Hasenhuttl insists management is partly about being one step ahead of the opposition.
The Austrian added: "It is a little bit like chess, who makes the better next move, that is the crucial managing stuff you do all of the day, think about what does he think? What can you change if he does this? It is nothing new."
Burnley manager Sean Dyche said: "I don't really know what the noise is about at the end of the day.
"I'd much prefer it to be sorted out on the pitch than I would bother about someone snooping around the training pitch."
Brighton boss Chris Hughton said: "I don't think it's right, but everybody will think differently."
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