Reverend Ian Paisley and his wife Eileen claim in a BBC television documentary aired tonight that he was edged out as leader of the DUP and head of the Free Presbyterian Church.
Dr Paisley, 87, said of his successor in the DUP, Peter Robinson, that "his ways are not my ways".
In an hour-long documentary on BBC Northern Ireland, Dr Paisley says he was forced into three key decisions in his political career: leading the DUP into government with Sinn Féin; stepping down as moderator of the Free Presbyterian Church and resigning as DUP leader and first minister.
Interviewed by journalist Eamonn Mallie, Dr Paisley and his wife vent their ire towards senior DUP figures including Mr Robinson, Deputy Leader Nigel Dodds and party chairman Maurice Morrow.
"They assassinated him by their words and deeds," said Mrs Paisley.
In a strongly worded statement, the DUP said the interview had harmed Dr Paisley's legacy.
It said while its former leader was entitled to his own opinions, he was not entitled to his own facts.
"He now seeks to place the responsibility for his decision on those who protected him most when, at 82 years of age, his ability to perform his duties was seriously diminished and causing widespread concern."
First Minister Peter Robinson said many would believe Dr Paisley's interviews would "do nothing to enhance his legacy".
"This is not the Ian Paisley we knew," he said.
Mr Robinson added: "Rather than return insult for insult, let me bless him with the mercy of my silence and wish him well."
Mr Dodds also expressed his sadness at Dr Paisley's comments: "Clearly the passage of time has diminished accurate recall of events," he said.
Dr Paisley recently spent a fortnight in hospital for tests and was released last week.