Mitchell has enjoyed a successful four years in charge since buying out previous co-owners Jeff Mostyn and Steve Sly, having presided over two promotions.
But, along with wife Brenda, they have now sold their share to the Russian businessman who has been involved with the club since October 2011.
In a statement released this afternoon, Mitchell said of his decision: "(It) has not been made lightly, nor without a great deal of angst, but the outcome will help enable the club to find the financial investment that it needs to keep moving onwards and upwards.
"We would both like to wish our partners, board members and successors the very best for the future and we sincerely hope that the club continues to enjoy its recent success going forward."
Director Josh Mitchell and associate director Dave Roberts have also relinquished their roles on the board with immediate effect.