Rafael Benítez's dislike of Sir Alex Ferguson manifested itself tonight in the Liverpool manager responding to another damaging setback to his side's aspirations of qualifying for the Champions League by demonstrating more bitterness towards the man who has become his nemesis in English football.

Benítez was aggrieved by the penalty that set Manchester United on the way to a 2-1 win, accusing Antonio Valencia of diving, and he referred to his previous accusations that Ferguson placed referees under pressure. "We know about the influence of Sir Alex in everything," he said. "I've seen three replays [from different angles] and the last one was suspicious. See the replay for yourself and how he fell to the ground." Asked whether he was saying it was a dive, he replied: "Yes, I think so. There is contact but the way he fell down – it was strange."

Television pictures showed the initial contact from Javier Mascherano had been outside the penalty area and Benítez was asked whether Ferguson had been trying to get into the mind of the referee, Howard Webb, when he talked on Friday of the Anfield club getting preferential treatment. "Just on Friday he said something?" he interrupted, his tone heavy with sarcasm. "Which Friday? This Friday or every Friday? Or every Friday of every year?"

Ferguson had written in his programme notes that he felt "a twinge of sympathy" for Benítez's current predicament, but the bad feeling between the two managers led to a confrontation on the touchline shortly after Wayne Rooney had scored his 33rd goal of the season, turning in the rebound after Pepe Reina had saved his penalty.

Rooney, recently troubled by a knee injury, left Old Trafford with a pronounced limp. His goal cancelled out Fernando Torres's fifth-minute header for Liverpool, with Park Ji-sung scoring the winner in the second half. "When you have different opinions you have to express those different opinions," Benítez said of that argument. "As you know, he [Ferguson] has his own opinion about everything."

Ferguson's argument was that Mascherano should have been sent off. "I thought the penalty kick was a red card," he said. "There was no way [Jamie] Carragher could have got across to stop Valencia from shooting, absolutely no way. He [Valencia] is too quick for Carragher to get across. It was a penalty but the law of the game is that if you stop a player from a goalscoring opportunity it's a red card, but not today it wasn't."

The United manager was unaware at that point that Benítez had spoken of Valencia being creative in his fall. "He [Mascherano] tugged him, and obviously I think the referee is right," Ferguson said. "He has got to play the advantage [after the first contact] because he was right through on goal and it wasn't until he was inside the box that he brought him down. So I think that was correct."

Benítez, however, was angered by what he perceived as several crucial decisions going in United's favour and said he was sufficiently concerned at half-time to tell Torres to keep his focus on the game. It was "not easy" for Torres, the manager reflected, and there was more heavy irony when he noted how Gary Neville's studs had connected with Maxi Rodríguez, leaving the Argentinian with a bloodied head. "I think it must have been a bird from the sky," he said.

Park needed a stitch for a facial gash, inflicted by Glen Johnson's boot. "A game like that, it's always been feisty," Ferguson said. "Both teams, with their pride and history, are going to compete. I don't think it got to a serious point at any stage."

While Liverpool are languishing in sixth, 18 points behind United at the top of the table, Ferguson's men have their sights on a fourth successive title, two points clear of Arsenal and four ahead of Chelsea, and have the added motivation of overtaking their Merseyside rivals with a 19th championship in total.

"We have been very consistent in the last two or three months," Ferguson said. "For periods of the game we played very well and in other periods we had to dig in and concentrate. It's always difficult to lose a goal and come back and win, it's a great quality that Manchester United have and it was that quality that won us the game again today."