Jurgen Klopp stoked the fire ahead of Manchester United's trip to Anfield next weekend by comparing penalty records after Liverpool were denied two spot-kicks in Monday's defeat at Southampton.
Danny Ings' stunning second-minute strike against his former club ended Liverpool's 12-game unbeaten run in the Premier League as the champions' winless run stretched to three games.
Klopp was aggrieved his side were not awarded either of their two second-half penalty appeals, with a Kyle Walker-Peters challenge on Sadio Mane and Jack Stephens' handball while blocking a Georginio Wijnaldum shot going unpunished by referee Andre Marriner.
Liverpool remain top ahead of Manchester United on goal difference despite suffering a second league defeat of the season, but the champions could be replaced as outright Premier League leaders by the time they welcome their rivals to Anfield on January 17 - live on Sky Sports - if United avoid defeat in their game in hand against Burnley.
It would appear the mind games have already begun ahead of the mouth-watering top-of-the-table clash, with Klopp questioning officiating over recent seasons, saying United "had more penalties in two years than I had in five-and-a-half years".
"If anybody ever again will say Sadio Mane is a 'diver', it's the biggest joke in the world," Klopp told Sky Sports. "This boy tries to stay on his feet with all he has. In two situations… other teams will get a penalty for it, let me say it like this. Then the handball, I don't know who will explain that to me."
Speaking in his post-match press conference, Klopp added: "We had a really good view of it [the Mane incident], and it looked like a clear penalty. I turned around to the fourth official and asked if it was going to be checked, he said it already had been and was not a penalty. That's 100 per cent true, and now someone wants to tell me how quick they had it in all these different angles.
"Last year, there was a penalty against Leicester when people said Sadio Mane goes down too easily - if he goes down easily, we would have had a penalty in this game and the last game, a stonewall penalty, but what Andre Marriner did with Sadio Mane I'm not sure if that's okay.
"The boy tried everything, had a few great challenges with Walker-Peters, but there were a lot of situations which should have been free-kicks. The last one, when he goes down, you see that back and in the box he hits him in the end with his left foot, that's a penalty.
"We cannot change. I hear now that Manchester United had more penalties in two years than I had in five-and-a-half years. I've no idea if that's my fault, or how that can happen.
"But it's no excuse for the performance. We cannot change it, we have to respect the decisions. But we can change our performance. That's our focus now."
Ref Watch: Neither incidents are penalties
Former Premier League referee Dermot Gallagher gave his verdict on Tuesday morning, and does not think either incident warranted a spot-kick.
He told The Football Show: "I watched the game live and I didn't think either of them were penalties. I thought the referee controlled the game pretty well, it ran without a lot of debate.
"I didn't think the Jack Stephens one was a penalty. What you have got to ask is does he put his hands out to block? No, you would expect his arms to be in that position. I don't talk about arms tucked into the body, I talk about the expected position for the arms to be.
"At that point, the defender is trying to block the ball, he's making his body shape to get to block that ball, he's not extending his arms. The ball also comes at a very short distance and very quick speed. There's no doubt it hits him on the elbow but I don't think any referee would give that as a penalty.
"I think this [Walker-Peters and Mane] is a tangle. Walker-Peters goes to make the challenge, I think he pulls out and Mane goes to skip the ball. You can see that they come together and I think it would be harsh to give a penalty.
"Walker-Peters is definitely going to pull out of the tackle, he doesn't want to get involved, he doesn't want to dangle a leg, which is what defenders are often accused of doing. He goes to tackle with his right leg and Mane actually goes into his left leg.
"The referee also couldn't be in a better position, so he has a perfect view of it. He can see the contact, how it's made - there's no doubt there's contact - and he says no. VAR quickly looked and agreed with the referee."
Carra: Mane initiated contact with Walker-Peters
Former Liverpool defender Jamie Carragher disagreed with his old club's manager and said Mane had made contact with Walker-Peters when the two came together, rather than the other way round.
Carragher said: "I think Mane kicks the back of Walker-Peters' calf. So that's where it could be a penalty, that side, but it's not. Mane hits the back of him.
"When you just see the other angle, he lets him come into the box, when you see the right foot come across from Walker-Peters, he makes a lunge for the ball with it. Normally when you see that, it's someone coming across to win the ball, they don't get it and they take the foot, or the attacker goes over it, the lazy leg, I've always called it.
"I've always said that's not diving, if someone puts a silly challenge, and you go over that foot if it's there. If that foot comes further across, maybe into this area, and Mane hits it, that's a penalty. But when he actually makes that challenge, you see his right foot is planted on the floor.
"He doesn't go far enough to make the challenge, he half pulls out of the challenge, and as we saw on the earlier one, it's a case of Mane half kicking his calf so I don't think it was a penalty."
Klopp: Liverpool enduring 'rusty' moment
Liverpool's recent struggle for form has seen them draw at home to relegation-threatened West Brom and away at Newcastle before their latest defeat on the south coast, and Klopp labelled his side as "rusty" after getting off to the worst start at St. Mary's.
"The slow start cost us, that made life massively difficult tonight," he said. "All these things can happen; we are human beings. As great at the set-piece [for Ings' goal was] we knew they could do it and the player there who missed the ball, and then the next one was a great finish, but we could have defended it.
"This was a rather rusty moment; we have to admit that. You can only solve a problem if you know the problem, and we are not blind to our problems. We have to fight and play through this, it's up to us to change that."
Tearful Hasenhuttl: A perfect start to 2021
By contrast, Southampton manager Ralph Hasenhuttl fell to his knees in tears after breaking a six-game losing run and taking points off Liverpool for the first time.
"I've never taken points against Jurgen so far, I think I started believing we could do it in the 92nd minute, not earlier," he said. "You never know, they are so strong in front, and you always think something can happen.
"The way we defended today was amazing, I think the effort the guys put in, everybody, was the key of winning. The mentality was maybe even better than against most of the teams.
"It's a perfect start to 2021. No one expected to take points against them today, we have 29, we are on our way and let's keep on going. It was an important step forward."