Liverpool manager Jurgen Klopp said the referee’s performance was affected by an assistant referee’s mistake for Sadio Mane’s goal against West Ham.
Mane’s opener stood despite James Milner being offside in the build-up.
Michail Antonio equalised for West Ham before the break but Klopp says referee Kevin Friend “did not want to open the gap any more” in the second period.
“I heard our goal was offside, I’m pretty sure the ref knew that,” Klopp told BBC Sport after the 1-1 draw.
“In 50-50 situations it was always a free-kick for the other team, which was hard and did not make life easy.”
Speaking to Sky Sports, the German added: “As a human being, if I know I have made a big mistake in the first half, I don’t want to open the gap any more.
“Referees are obviously human beings, and I understand that, but I didn’t during the game because I had no clue that our goal was offside.”