A statement released to the Stock Exchange was published on the club’s official website hours before the second leg of their Champions League play-off clash with Malmo in Sweden.
The statement read: “The directors of the company wish to announce the resignation of Eric Riley as financial director of the company, with effect from 31 December 2015.
“Eric, who was diagnosed with Parkinson’s Disease and prostate cancer in 2011, has been finance director for over 21 years.
“To assist with a smooth transition to a new financial director, with effect from 1 January 2016 Eric will be appointed as a non-executive director of the company.
“Eric will fulfil this role until 30 June 2016 at which point he will step down as a non-executive director of the Company.
“The Company is in the process of identifying and recruiting a suitable replacement for Eric as financial director and will make further announcements in this regard in due course.”
Club chairman Ian Bankier said: “We would like to thank Eric for his huge commitment to the company as financial director.
“During his time here he has played a vital role in the development and growth of the company, and has also made a very meaningful and unstinting contribution to the successful promotion of the game in Scotland.”