Manchester City boss Pep Guardiola says he has "never had doubts" about the integrity of Premier League referees.
It comes after Nottingham Forest issued an angry post on social media criticising officials following their 2-0 defeat at Everton on Sunday.
Forest said they were "considering their options" over "extremely poor" refereeing decisions.
"They do their job as best as possible," Guardiola said.
"When they do the job, they want to do it well. The game is so difficult. It is fast and quick. Decisions have to be made in one instant. It's not easy."
Forest were furious after three penalty appeals were rejected at Goodison Park, with defeat leaving the club just one point above Luton, who sit in the relegation zone.
Shortly after the game, Forest said they had "warned" refereeing body Professional Game Match Officials Board (PGMOL) that "the VAR is a Luton fan but they didn't change him".
On Monday, the club called for the audio between video assistant referee Stuart Attwell and on-field official Anthony Taylor to be released publicly.
It later emerged that Forest will be offered the chance to hear VAR audio from the three penalty claims in private.
Speaking in a news conference on Wednesday, Guardiola said of referees: "They feel the pressure, we put pressure on them for the passion of the game, for the moment.
"When I sit here and reflect they try to do their best and are under scrutiny with the cameras there."
City head to Brighton in the Premier League on Thursday before travelling to face Forest on Sunday.