VAR officials must be wary of 'wrong kind of solidarity' with referees, says Fifa's referees' chief Pierluigi Collina
Video assistant referees must not show the "wrong kind of solidarity" with colleagues by failing to correct their mistakes, says Pierluigi Collina.
VAR oversaw three penalty decisions in Thursday's Premier League games and all were later deemed to be incorrect.
Collina, Fifa's referees' chief, has called for consistency in the use of VAR all over the world.
"If you belong to a team, you always try to protect your team-mates," said the 60-year-old Italian.
"If your team-mate made a mistake, you try to find everything to say 'no, no, no, he was correct'."
Fifa has taken over the implementation of VAR from the game's law-making body the International Football Association Board.
Collina warned of a "sort of wrong idea of solidarity" and wants referees to use pitchside monitors to review decisions.
"It's a sort of friendship I would say," he told the World Football Summit.
"Referees must understand the solidarity and the friendship that they want to show is to tell their colleague, 'Be careful, you might have made a mistake - it's better that you have another chance watching the incident on a monitor, you have assessed probably wrongly,' so that finally you can avoid a mistake."
In Thursday's Premier League games, Bruno Fernandes won a spot-kick which he scored in Manchester United's 3-0 win over Aston Villa, James Ward-Prowse hit the bar after a disputed penalty as Southampton drew 1-1 with Everton and Tottenham should have had a penalty for a Joshua King shove on Harry Kane in a 0-0 draw with Bournemouth.
Ex-Premier League official Dermot Gallagher advised that United and Southampton should not have been given penalties, but Tottenham should have been awarded one.
What do the managers say?
Arsenal boss Mikel Arteta: "I never have any concerns about the intentions of the referees. Now everything is so professional, dedicated and they are under so much pressure and criticism.
"I know they try their best with the decisions they have to make. They are getting more and more complicated because of the speed of the game, how quickly they have to react and the pressure with the new system of VAR. We are here to support them. We need them.
"I'm sure they have the right intentions but at the end of the season there is something that has to go into debate and I agree certain principles are going to apply so at least every decision will have the same level of determination."
Tottenham manager Jose Mourinho: "I think you should have access to them [VAR officials]. I think you should have access to them to ask directly, 'Why?'.
"It is very important. They are very important in the game. It would stop nothing, make things much more open, much more clear.
"It would give the ref the chance to say, 'Yes, I made a mistake - I feel sorry for that', or, 'Yes, I had an incredible performance'."
Liverpool boss Jurgen Klopp, on the penalty awarded to Manchester United: "I can 100% see that [Aston Villa manager] Dean Smith is struggling to accept what happened last night.
"It should just be the right decision. What I don't understand is overruling is so complicated that it must be a clear and obvious mistake. It's difficult but I didn't think last night was too difficult. It's obviously not good.
"I really would like to think that three people watch it - a ref, the VAR and another VAR - and they should find the right decision in the end."