Former NSW coach Gould called into question Grant's repeated chat with referee Ashley Klein in seeking penalties and set restarts, ahead of Wednesday night's State of Origin decider at Suncorp Stadium,
Maroons legend Cameron Smith said it was all about the need to "keep referees honest" but Gould went further.
"Let's call it for what it is – Harry is a cheat," Gould said on Monday night's 100% Footy program on Channel Nine.
"When you do that to a referee, and you're talking to a referee, and questioning a decision, you never think he's going to reverse a decision. It's about what he does with the next one."
Smith agreed that speaking to referees in such a manner concerned "what he does with the next (decision)" before Gould reasserted Grant was "a cheat".
Slater threw his full support behind Melbourne captain Grant and resisted inflaming the situation.
"We haven't got an issue with the referees," he said.
"Harry's had a great week. Harry's ready to go.
"Harry will be concentrating on playing footy and that's what they do out there. He's an integral part of our footy team."
Asked whether it was important in Origin to keep referees onside and build a rapport, Slater was emphatic.
"Not as important as playing the game. That's where our focus is," he said.
Meanwhile, 14-game Maroons regular Carrigan has made a stunning recovery from ankle surgery and is set to play his first game since Brisbane's May 31 loss to St George Illawarra.
Carrigan, who missed Queensland's 44-24 win at the MCG in game two, had declared himself a certain starter during camp, but training is mostly closed off from public view.
Slater said the Broncos powerhouse had gone above and beyond in his recovery.
"He's in a great spot. He hasn't missed a session," Slater said.
"In fairness, he's done more.
"He ducked into the Broncos on the Monday before coming into camp to get through some of his rehab work and he's in a really good spot.
"Anyone who knows Patty knows he's as professional as anyone in the game. He's ready to go."
