Speaking for the first time since Leeds blew the lid on Hardaker's indiscretions that prompted his withdrawal from his World Cup squad, McNamara claims the England management staff were fully involved in the process to sanction the player.
McNamara has been widely criticised for how he has dealt with the latest incident in a series of off-field mishaps which have dogged England's World Cup campaign to date.
The coach initially responded to speculation that Hardaker had been involved in a drunken brawl by claiming he was ill and told a BBC interviewer that the media "are just making things up to try and disrupt my squad".
Two days later England announced Hardaker's withdrawal from the squad, citing "personal issues", but on Wednesday Leeds issued a statement revealing their player was in breach of the club's code of conduct for players.
The Rhinos fined Hardaker £2,500, issued a written warning and ordered him to report for pre-season training on November 25.
Leeds chief executive Gary Hetherington, who carried out his own investigation into Hardaker's actions, said he had nothing to add to his statement but McNamara said he supported the Rhinos stance.
"We have worked closely in conjunction with Leeds," McNamara told a press conference at the KC Stadium, where England are expecting close to a full house for their final group game.
McNamara insisted the withdrawal of Hardaker, which followed the earlier expulsion of Gareth Hock for breaking an alcohol ban and failing to turn up for a recovery session, has not caused any disruption to his preparations for the Fiji match.
"I said earlier in the week that, as a coach you have to deal with various situations, whatever arise," he said. "That's been dealt with.
"Unfortunately (Hardaker) couldn't reach the standards that were set within the group. In conjunction with Leeds, the matter has been dealt with."
For Saturday's game McNamara has recalled hooker Michael McIlorum, who was thought to be one of the players involved in the original disciplinary breach featuring Hock, but McNamara remained tight-lipped over his recent past while extolling his present virtues.
"It's a great opportunity for Mickey," McNamara said. "He's a tremendously tough player.
"He's an aggressive type of player who probably brings a little bit into the middle area that we were down on a little last week."
Although Fiji have a wealth of proven talent in their backline, McNamara expects their strength to come from a pack that includes former Kangaroo stalwart Petero Civoniceva and the trio of Sims brothers.
"It's a huge game," the coach added.
"We're playing a side that is physical. They've certainly shown the way in that department in this tournament.
"They've got some very experienced players in the majority of positions and they've an exciting team to watch and one that will bring the best out of ourselves.
"Their back five is as good as it gets."
After opening up with an encouraging display in a close-fought defeat by the Kangaroos, McNamara is expecting his side to produce their best performance of the tournament so far to take them into a quarter-final with either Samoa or France.
"I'm really excited by this week," said McNamara, who once more played down the effects of any disruption caused by the withdrawal under a cloud of Hardaker.
"We did enough last week to beat Ireland but I think this week will see a step up in our intensity."
England are boosted by the return from suspension of Sam Burgess while McNamara has recalled Wigan prop Lee Mossop and captain Kevin Sinfield is confident his pack will be a match for their opponents.
"I think we've got great big side that can be physical when it wants to be and I hope we can show that tomorrow," Sinfield said.
"We're expecting a physical battle and we've worked really hard in that department this week, as you can tell from my looks."
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