John Gregory is in the process of launching legal action against Derby for his "premeditated and dishonourable" dismissal.
The Nationwide Division One club today confirmed his sacking after an appeal to the club was rejected following his formal dismissal on May 9th following "serious allegations" against him.
But Gregory will challenge the decision by the club's board and is in the process of taking his case to the High Court for wrongful dismissal and payment of outstanding wages.
A statement released by his solicitors read: "The decision by Derby County Football Club to dismiss John Gregory for serious misconduct was clearly premeditated and dishonourable.
"It was done despite compelling evidence that he had done nothing wrong whatsoever.
"Over the course of three days of hearings we submitted evidence including documentary evidence running to over 400 pages which proved that John Gregory was innocent of all the allegations against him.
"As has been widely reported in the press, John Gregory has a clause in his contract which entitles him to substantial compensation from Derby County if his contract were terminated.
"The justification for his dismissal was always a device by Derby to try to avoid honouring their contract with him by paying the compensation.
"Today we are beginning the process of High Court proceedings for payment of John Gregory's contract in full and damages for his wrongful dismissal.
"John is looking forward to having the opportunity to have his case determined by a fair and independent judge."
Gregory, who was unveiled as Rams boss in January 2002 with a brief to keep the club in the Premiership, was formally dismissed earlier this month having been suspended in March, but lodged an immediate appeal which was heard by the club last week and then rejected yesterday.
A statement released by the club read: "Chairman Lionel Pickering has considered the submissions made by John Gregory and his advisors at his appeal and has concluded the result of the original hearing should stand.
"As a consequence, the decision to dismiss John Gregory from his role as Derby County manager stands.
"The club will not discuss this matter in any further detail."