The leak occurred while Barker was in negotiations with Team New Zealand top brass. It is understood one of the options being discussed was for Barker to be replaced as skipper, but to retain a leading role within the team.
That now appears unlikely, with the Herald on Sunday learning last night that Barker - left in tears after Team NZ's heartbreaking loss to Oracle in the 2013 America's Cup - is set to walk away from the crew if Dalton remains in charge of the syndicate.
A source close to the team said if Barker moves on he will reject any imposition of a gagging order and is preparing to reveal all.
"He wants his chance to share his side of the story and New Zealand deserves to hear it," the source said.
The explosive legal move comes as a source close to Barker told the Herald on Sunday the yachtsman was struggling to come to terms with how his likely axing was made public.
"Dean is having a hard time. It's not easy for him at the moment, we're talking about 20 years of service," the source said.
"It's all a shock that this has come out in the media, that he has not been told, but it has been leaked - and Dean has a good understanding of who this has come from.
"I do not know why he [the leaker] would want to do this, or what good this actually is doing for Team NZ. It's a total mess. The history and brand of Team NZ is being destroyed.
"The way this is being handled, Team NZ is at risk of losing Dean altogether.
"And that is just completely nonsensical."
Barker and Dalton did not respond to interview requests.
And Team New Zealand chairman, Dr Keith Turner, was also tight-lipped, describing the Barker situation as "off limits".
When asked about the legal letter, he responded: "I am not commenting on anything to do with any member of the team."
The syndicate is also under financial pressure as sponsors consider whether a regatta in Bermuda will bring them any benefits. The Government is also yet to formally confirm it will fund another campaign.
The Herald on Sunday yesterday sought the opinion of the syndicate's prime 2013 campaign sponsors - Emirates, Nespresso, Toyota, Camper and Omega.
Only Toyota responded, with assistant manager of digital marketing and communications Morgan Dilks unable to say if the company would be part of the syndicate's next campaign.
"We haven't heard anything official from Team New Zealand and until we do we are not in a position to comment," he said.