Jets coach Ernie Merrick has urged A-League officials to stop referees speaking to players in foreign languages, saying the "confidential conversation" will create "mayhem".
Merrick was fuming on Saturday night after Newcastle had a "blatant" penalty decision go against them in the 22nd minute of the 1-1 draw with Perth Glory at McDonald Jones Stadium.
When asked at the post-game press conference if he had spoken to referee Jonathan Barreiro about the decision, Merrick said: "When he wasn't speaking Spanish, yes I spoke to him.
"He speaks a lot of Spanish during the games and talks to the opposition a lot in Spanish. We're in Australia, I would have thought he would be speaking English most of the time so we can all hear what he's saying to his mates."
On Monday, Merrick expanded on the issue and asked: "When is that going to stop?"
"He speaks in Spanish to players, which means it's a confidential conversation, and I don't think that's appropriate.
"This is an English-speaking country, everyone speaks English, apart from [Jets striker Abdiel] Arroyo, and I think he should speak English so we all know the instructions or details that he is giving to Spanish players.
"When is that going to stop? So now we have a Greek referee, or from a Greek background, speaking to Greek players in the Greek language and the same with Macedonian, Croatian. Where does that stop?
"So it's either all English or it will become mayhem.
"And you remember what the old NSL days were like, and we don't need to go back there."
Merrick's frustration came as the Jets remained winless in four games after Spaniard Diego Castro equalised in the 86th minute.
Newcastle are second last on two points and face in-form newcomers Western United away on Saturday night in round six.
The Jets have scored just four goals in four games and will be missing Arroyo (Panama), Matt Ridenton (New Zealand) and Bobby Burns (Northern Ireland) to international duty this weekend.
Merrick was looking to the likes of Jason Hoffman, Nick Fitzgerald, Dimi Petratos and Angus Thurgate to carry the goal-scoring load against Western United, who are second on 10 points after three wins from five games.
"I think there's a few teams going through this," Merrick said of the Jets' poor conversion in front of goals.
"They are creating a lot of opportunities. I'm thinking of when Sydney played Wanderers, a couple of games Victory have played where they dominated the stats and not scored, and Perth Glory.
"So I believe the defences are much stronger ... I think teams are defending in a much more organised fashion. But over the season you will find the strikers will start finding weakness, there will be better quality goalscorers up front, there will be players coming back from international duty or from injuries.
"That will change the quality of games up front, but I think it's good all around that all teams are very competitive."
Merrick said captain Nigel Boogaard (groin) was a "60 to 70 per cent" chance of returning on Saturday night.