Mr Sharif stepped down on July 28 after the Supreme Court disqualified him for not disclosing his assets. After the verdict, he ceased to be a member of parliament.
He, however, continued as the president of PML-N.
Election Commission of Pakistan (ECP) through the notice told the PML-N that Mr Sharif cannot lead the party after disqualification under the Political Parties Order 2002.
The ECP also referred to the constitution of PML-N which mandates that the party would appoint its new chief within one week. It asked the PML-N to elect a new president and inform the election commission.
The PML-N was already holding consultation to appoint new party chief.
There are reports that Mr Sharif's younger brother Shehbaz Sharif might be appointed as new president of PML-N. There are also chances that former first lady Kulsoom Nawaz may be given the role to lead the party.