Leeds United boss Marcelo Bielsa admits he spied on Sheffield United and Sheffield Wednesday earlier this season

The so-called '˜Spygate' affair, in which a man employed by Bielsa was caught and escorted by police from Derby County's training ground before their match with Leeds last week, took a twist on Wednesday when the manager called an impromptu press briefing.

During that, the Argentine suggested that the incident involving Derby was not a one-off and that he had been watching training sessions of all the Championship teams his side has faced this season.

He said: 'I observed all the rivals we played against and watched the training sessions of all our opponents before we played against them.

'Many people have condemned the behaviour saying it was immoral and affecting fair play, saying that it was cheating, many managers and ex-players thought my behaviour was disrespectful.'

Leeds played Wednesday in September 28, drawing 1-1 at Hillsborough with Mat Klich equalising an Adam Reach opener.

They traveled to Bramall Lane on December 1, winning 1-0 after a late goal by Pablo Hernandez following an error by Blades goalkeeper Dean Henderson.

United are currently challenging Leeds for a promotion place, with Chris Wilder's side in second place in the Championship, four points behind their Yorkshire rivals.

Earlier this week, Wilder had his say on the affair and refused to condemn his opposite number at Elland Road.

"It's been over exaggerated," Wilder, whose side visits South Yorkshire in March, said. "It's not something that we would do but I think the manager has been clever because the chant about Leeds United ('We all hate Leeds') will get a little bit louder now and they will love that siege mentality.

"You saw in their performance (against Derby), that it was them against the world, and I thought they were outstanding with it."

On Tuesday the Football League released a statement saying that they were to carry out an investigation into last week's incident, a factor in Bielsa calling the press briefing.

'The EFL has today written to Leeds United requesting their observations in regard to an incident that took place in the vicinity of Derby County's training ground on Thursday 10 January, 2019. It follows a complaint from Derby County who allege that an individual, acting under the instruction of Leeds United, sought to observe a private training session the day before the two clubs were due to meet in the Sky Bet Championship.

'The EFL has now determined that it is appropriate to consider this matter in the context of a number of EFL regulations whilst also noting that the alleged actions appear to contravene the Club's Charter that all EFL clubs agreed to in summer 2018.

'The decision to progress this matter to a formal investigation comes as a result of the club's manager, Marcelo Bielsa, admitting to instructing an individual to undertake the acts being complained of in a television interview broadcast on Sky Sports on Friday, January 11, 2019.

'The Football Association has also confirmed they are considering the same matter in line with its own rules and the EFL will work with its FA counterparts to ensure that any potential action taken does not prejudice those investigations being undertaken.'