Former Health Minister Jim Wells has claimed the DUP "sat by and watched" as he was "set up for a very public downfall", and did not "lift a finger to help".
In a strongly-worded email to DUP official Richard Bullick, Mr Wells said he views himself as having three options - resigning from the DUP, being reappointed as Health Minister or publicly declining the offer of reappointment.
The South Down MLA resigned as Health Minister in April after he was caught up in a storm following remarks he was alleged to have made during an election hustings event ahead of the Westminster poll.
Earlier this month, the Public Prosecution Service said he would not be prosecuted for the comments.
Mr Wells recently described the last five months as "the most difficult" of his life and confirmed he was taking a two-week break to "recharge his batteries".
He revealed to the Belfast Telegraph earlier this month that he shielded his seriously ill wife Grace from the full extent of what he has been going through, and said she does not know he is no longer Health Minister.
Mrs Wells remains in a care home where she requires round-the-clock care after suffering two devastating strokes earlier this year.
Yesterday an email, which was inadvertently leaked to the media, reveals the full extent of Mr Wells' frustration with his party, the DUP.
He accused the party of not helping him to clear his name.
"I am now to believe that I have lost the confidence of the party officers and as a result of this, the Press officer team were either instructed or permitted to do every thing possible to prevent me clearing my name," he wrote.
"I should add that despite this I have kept the Press officers completely up-to-date with developments and invited them to come alongside me to help. Their reluctance to do this is very telling."
Mr Wells went on to claim that "despite the valiant attempts by the Press office to thwart my efforts to clear my name, I believe that as a result of my own actions, I have gone some way to achieve this".
The South Down MLA said despite how he feels he has been treated by the DUP, he "defended its position on Nama" at the finance committee.
He set out the three options that he feels are open to him, saying that resigning from the DUP would give him "free rein to clear my name".
The second option he saw of being re-appointed as Health Minister did not appear to appeal to him, because he said he felt he would hold this position "knowing I no longer have the support of the party officers or the Press team".
He added on the possibility of being reappointed Health Minister: "I also believe that there is no chance whatsoever that this will happen.
"The party sat idly by and watched one of its ministers being set up for a very public downfall. It then stood on the sidelines as the evidence emerged that he was innocent of the allegations made against him and decided not to lift a finger to help."
Mr Wells said that his "vindication" would be almost complete if party leader Peter Robinson publicly offered him the opportunity to become Health Minister again, and he turned it down.
Neither the DUP nor Mr Wells have publicly commented on the contents of this email, which is dated Tuesday, October 20.