Powell was angry with his players for their poor showing, but was particularly annoyed by Child, as well as for having a try disallowed in the second half of the game.
“It was a terrible decision. It was one of a number of decisions which were pretty poor,” he said.
“He was a poor referee, a pretty arrogant referee. It was as disappointing a performance from him as it was from us.
“It was a big game and we just turned in a performance that was way off the pace and not good enough.
“I keep saying that we’ve got a lot of work to do, but not a lot of time to do it.
“We’d have got beat anyway, I’m not blaming the referee for that. I just don’t think he should be refereeing at this level.”
Powell now wants to see a positive reaction from his players, who seem to be struggling to find form after losing in the Challenge Cup final to Leeds at Wembley.
“The boys have got to respond, they’ve got to lift themselves,” he said.
“We’ve got to all work hard as a coaching staff, but I’m looking for the players to really grow and have a pop at it.
“We either limp out, or we can charge at the game.
“I think ultimately as a group all of us have got to take responsibility.
“We haven’t played well since Wembley. I don’t know if that’s the only reason, but it’s obviously a significant one.
“We’ve got to try and find our groove again, and I don’t think it’s going to be easy.
“We’ve got one last shot at it next week to see if we can do anything about it.”