The Italian took ownership of the Championship club last February, only to be disqualified the following month when a court in his homeland found him guilty for the non-payment of import duties on a boat.
Cellino successfully overturned that Football League ruling last April, but was subject to a new disqualifying condition after the full disclosure of documents from the Italian court was made available, and he was demanded to resign within 28 days.
A fresh appeal was launched to the Football League's Professional Conduct Committee (PCC) and it was announced last month that the former Cagliari owner was permitted to remain as a club director of Leeds until the case was heard.
However, the original ruling was upheld and so Cellino was disqualified from acting as a "relevant person" as per Football League regulations until April 2015.
Mr Cellino said in a statement on the club's official website: "It is with great sadness and frustration that I have to take this step, however I abide by the Football League's decision to temporarily disqualify me from this great football club and will return in April in good health and good spirits.
"I have done my best for a club and fans that I hold close to my heart and it is now financially much stronger than it has been for a long time. It will continue to thrive and I am sincerely looking forward to returning very soon."
Leeds revealed that lifelong Leeds supporter Umbers will take over as chairman in Cellino's absence.
Cellino said: "Following my resignation and in my temporary absence, the board has appointed Andrew Umbers to become chairman of Leeds United.
"Andrew has personally worked tirelessly with me in restructuring the football club from May 2014 and shares the same goals, strategy and insights that I do in bringing Leeds United back from its financial abyss to make it the strong entity that its fans, players and city need it to be and to which these foundations are now in place.
"Andrew is also a Yorkshireman and lifelong Leeds United fan."
