The Gunners boss was adamant that there were two offside incidents in the build-up to Ivan Toney’s 74th-minute header.
Mason, who retired from refereeing to become a full-time VAR in 2021, was briefly relieved of his duties by the Premier League earlier this season following two decisions which were ruled to be incorrect by a review panel.
The first was to rule out a Newcastle winner against Crystal Palace in September and the following day he also wrongly disallowed a Gabriel Martinelli goal for Arsenal at Manchester United.
He said: “I’ve looked back at the goal and it was offside. They haven’t explained why it wasn’t ruled out and we’ll be giving our views to the Premier League.
“You have to apply certain principles in defending set-pieces and you do that by sticking to the rules.
“But apparently they were not applied and if you suddenly change those rules you tell us before the game so you don’t defend with the line so high.
“We apply what the referee tells us every single week before the game – that if the blockers are offside then
“I also think their player was offside when he crossed the ball. I was hoping that the cameras and visuals would pick that up because it looks like there were two actions.
“But it’s too late and now we’ve dropped two points.”
Even Brentford boss Thomas Frank admitted: “I agree that when we took the free-kick, Pinnock is an offside position.
“Then, as far as I understand the football laws, the next question is did he influence the cross?
“VAR decided it was not enough to rule out the goal and I agree.
“But every week there are VAR decisions that go marginally one way or the other.”
Goal-scorer Toney said: “I saw Christian Norgaard was onside but I don’t know about Ethan Pinnock.
“They said it was further on and VAR gets messy. I was just hoping it was going to be allowed and it was.”
Arsenal fans argued that Norgaard was offside as he hooked the ball across the face of goal for Toney to head home.
One even went as far as suggesting that the Gunners should demand the game be replayed.
They wrote on Twitter: “@Arsenal needs to appeal and request a replay. When the title is so close, Brentford players were offside twice!”
Meanwhile, other fans were left raging by the fact the goal stood.
One wrote: “Ridiculous. Norgaard looked offside.”
A second said: “How isn’t that Norgaard offside FFS.”
And another aggrieved account fumed: “Blatant offside for Brentford’s goal but yeah no surprise every decision goes against Arsenal.”
If second-placed Man City beat Aston Villa, they will have the chance to knock Arsenal off the table with victory at the Emirates on Wednesday night.
Yet Arteta insisted: “I think it was a really strong performance from my players. I’m delighted with how the boys tried and how much they wanted the win.
“We discussed today about not giving Brentford any set-pieces because that is their biggest strength.
“We controlled them quite well but unfortunately they scored from an offside position and that has cost us points.”