Benitez hits back after touchline spat with Ferguson

However, the Reds boss did not think Sir Alex Ferguson's pre-match suggestion that Liverpool benefited from many decisions other sides did not had a bearing on Yorkshire referee Howard Webb's handling of the game.

Striker Fernando Torres gave the visitors the ideal start when he headed in Dirk Kuyt's cross six yards out in the fifth minute.

However, referee Webb controversially awarded a penalty five minutes later when Valencia went down under Javier Mascherano's challenge despite initial contact being outside the area.

Wayne Rooney converted the rebound after Jose Reina had brilliantly saved his spot-kick but it was not until midway through the second half when Park Ji-sung scored the winner from a diving header.

In the last minute Torres had a chance to equalise from 10 yards but ballooned his strike into the air and Yossi Benayoun headed tamely into goalkeeper Edwin van der Sar's arms.

"We gave away the penalty too early – but there are doubts about the penalty," said Benitez. "When you see the replay it is suspicious how he went to the ground."

Asked whether he thought Valencia had dived Benitez said: "From the replay I think so. It is not clear but the way he fell down... it is strange.

"It made a big difference. We were playing well and had confidence and then one situation changed everything."

Benitez was involved in a heated touchline exchange with Ferguson after Rooney's goal, with his United counterpart suggesting Mascherano should have been sent off.

However, the Spaniard did not believe Webb had been influenced by Ferguson's comments prior to the game.

"Some decisions in the past have not been the best for us but I consider Howard Webb a good referee," he added. "The referees are professional. We know the influence of Sir Alex in everything but he is a good referee.

"Jamie Carragher was coming inside so he was in the middle of the action (and therefore Mascherano should not have been red-carded)."

Of their touchline exchange Benitez said: "When you have different opinions you have to express them. He has his own opinion about everything."

Ferguson's opinion differed from that of Benitez.

"I thought it was a red card," he said. "There was no way Carragher could get across and stop Valencia from shooting – he is took quick for Carragher to get across.

"The law is if you stop someone from having a goalscoring opportunity it is a red card. Not today.

"The referee was right, he tugged him down. He didn't bring him down outside the box; he didn't go down until he was inside the box. The decision was correct."