In a statement, the fiery Italian cited "a number of broken promises" and claimed his position had "become untenable" with continuing uncertainty over the club's ownership. The former West Ham striker had issued a statement at the start of this month revealing he was considering his position following the sale of Matt Ritchie to Bournemouth.
The 44-year-old, who guided the Robins to promotion last season, claimed he had tendered his resignation last Tuesday but had met with the club's prospective new owners on Friday.
As a result of those discussions, Di Canio revealed he agreed to stay on as Swindon boss only to make another U-turn with this announcement on Monday as a takeover was still yet to be rubber-stamped.
In the statement, Di Canio said: "Last Tuesday, 12th February, I formally confirmed my resignation as manager of Swindon Town Football Club with immediate effect. 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 three 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. 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 club's 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."
Source: PA
Source: PA