In his new book Legacy, Tietjens accuses Hansen and All Blacks assistant coach Ian Foster, along with New Zealand Rugby boss Steve Tew, of not giving him the support he needed to lure the likes of Ben Smith, Ardie Savea and Beauden Barrett across to the national sevens team for the Rio campaign.
New Zealand failed miserably at the Olympics after they were knocked out by Fiji at the quarterfinal stage.
Tietjens questioned the governing body's leadership in a year when it publicly stated Olympic gold for both the men's and women's teams were dual priorities.
At a meeting attended by Tietjens, along with Hansen, Foster, Tew and high performance manager Don Tricker, the veteran sevens coach wrote in his book that he suddenly realised he was not getting the support he needed from those involved in New Zealand Rugby.
"When we talked about Beauden Barrett, I asked if anyone could tell me why a guy who seemed so keen initially had now completely changed his mind. Neil Sorensen looked at Ian Foster and asked him what he had talked to Beauden about. Ian said he had never told him he couldn't play sevens; he had only outlined a list of things he needed to work on in the fifteens game.
"I eventually left the meeting feeling completely isolated and that no leadership had been shown there. NZR had a documented strategic goal that proclaimed gold medals in the men's and women's sevens competition to be the number one priority in the 2016 season."
After touching down in London with the All Blacks, Hansen said he thought Tietjens was offering up excuses.
"He's got to sell his book so he's got to put something of interest in there," he said.
"Yep, I did say why does Ben Smith have to play four tournaments? I thought he could've played one or none he was that good. That's the only way he was going to go because he didn't want to leave the Highlanders.
"That's what we tried to explain to him [Tietjens] and he made the choice himself. I'm not sure why he's saying there was no leadership – the leadership falls on his head. The conditions of Ben Smith playing – coming from Ben Smith himself – were that he was available but he didn't want to play four tournaments.
"When he [Tietjens] heard that he made a decision. It's his decision to make. No-one else interfered with that decision. I think he's looking for excuses personally but it'll sell a few books I suppose."
Photo by: JOHN COWPLAND/PHOTOSPORT (Caption: Sir Gordon Tietjens has now taken up a role with Samoa after parting ways with New Zealand Rugby)