"It was a wrong decision, poor decision, as simple as that," McNamara said.
"As I believe was the decision not to send off Tony Williams. That was a dead-set red card. No two ways about that.
"We would never ever use the officials as a reason why we never won that match this week.
"But the unfair influence at the start of the week by Tim Sheens and the rest of his staff - the pressure that that referee must have been put under - I think is wrong.
"For me it is a straight send-off as he has hit him right across the top of the head and it is a sending-off offence.
"We had Adrian Morley sent off a few years ago about 16 seconds in, there are a lot of examples. Shaun Edwards quite a few years back on this same ground."
Sheens denied McNamara's claims, and said his comments earlier in the week were only outlining his disappointment at the way English referee Phil Bentham refereed his side's win over New Zealand last week.
"I didn't talk about the referee at all. I spoke after last week's game that I was disappointed in that particular game," Sheens said.
"I have said nothing in that respect about this week's game."
"I don't think it was a send-off, but of course I am the Australia coach."
Williams, who scored one of his side's six tries, denied the challenge was intentional and said he and Westwood had spoken after the game and there were no hard feelings.
"To be honest, I hit his shoulder and I slipped. I don't think there's anything wrong with that," Williams told AAP.
"It was accidental and that is all it was, their players didn't say anything to me at the time, me and Westwood swapped shorts at the end of the game, and it's all good."
Luke Lewis, Paul Gallen, Chris Lawrence, Darius Boyd and Greg Inglis also scored tries as the Kangaroos booked their place in the final.
However, their hopes of winning the tournament for the first time since 2009 received a huge blow when Billy Slater broke his collarbone in the 11th minute.
Slater will now miss the rest of the competition.
The flying fullback must now decide whether to have surgery in the UK or Australia after a planned procedure was cancelled at a private hospital in London.
"It's a fairly straightforward operation, but it is a very painful injury," Australian physio Tony Ayoub told AAP.
"He should be back in time for the new NRL season, the rehab time is about eight weeks."
Sheens' side will play the winner of New Zealand and England, who meet in Hull next Saturday, in the final.
The Kiwis beat Wales 36-0 in the first game of Saturday's double header.
- AAP
