The former West Ham United striker has ended his tenure with the League One club after taking over in May 2011, stating that his position had become untenable after 23-year old winger Ritchie was offloaded to Bournemouth on January 30.
"It is with great regret that I find myself having to make this further press statement," read Di Canio's statement released to the Swindon Advertiser.
"Last Tuesday, 12th February, I formally confirmed my resignation as Manager of Swindon Town Football Club with immediate effect.
"In my previous press statement on 1st February, I said that I was considering my future, as my position with the club had become untenable, after I found out that Matt Ritchie had been sold without my consent."
The statement continued: "As I had previously stated, there have been a number of broken promises made by the club over the time that I have been Manager of Swindon Town.
"Despite these problems, I have delivered everything and more that was asked of me, by achieving promotion last year as Champions and competing this season for promotion to the Championship and being just 3 points from top place a year earlier than expected.
"I did not resign immediately, nor publicise my resignation after I had formally confirmed it, as I did not want to jeopardise the negotiations for the sale of the club and I wanted to listen to what the proposed new owners plans were.
"Following discussions, my representatives put forward a proposal that would secure my future at the club until at least the end of the season and quite possibly beyond as well. This proposal actually reduced the Clubs contractual liabilities to me in the interest of saving Swindon Town FC. At a meeting last Friday the proposed new owners accepted and said they were very happy with the new terms.
"I entered into a temporary arrangement with the proposed new owners to continue in my role as Manager but all this was agreed subject to Football League approval for the purchase of the Club being granted by 5:00pm on Monday 18th February.
"At the time of issuing this statement, I have had no further contact from the proposed new owners and I have been told that unfortunately Football League approval has not been granted yet and therefore my temporary arrangement has ended and my resignation stands.
"This is all I wish to say for the time being other than to thank my Technical Staff and the players for their fantastic professional behaviour and attitude in achieving what they have done up to today, also thanks to the Swindon Town supporters for the incredible support they have shown me and the team throughout my time as Manager.
"I wish the best of luck to the supporters, the players and my Technical Staff for the future."