Senator Nasar's name had been approved a day earlier by former prime minister Nawaz Sharif after the proposal did not meet much resistance from party leaders, Dawn News reported, citing party sources.
It was agreed at the meeting of the Pakistan Muslim League-Nawaz (PML-N) central working committee in Islamabad, the report said.
The source was quoted as saying that the name for PML-N's permanent party chief will be decided upon on September 7.
Party's estranged former interior minister Chaudhry Nisar, however, expressed reservations over the fact that Nasar's name as Sharif's interim successor was leaked to the media even before the central working committee's meeting, the source said.
"Why was this meeting called if the decision was already finalised in Lahore," Nisar was quoted as saying.
The central committee also unanimously approved a resolution to name Sharif the party's 'quaid' (leader) while paying tributes to his services to the PML-N, the report said. On August 8, the Election Commission of Pakistan (ECP) had issued a notice to the PML-N for the appointment of a new party leader citing Sharif's de-seating and disqualification by the Supreme Court in the Panama Papers case.
The ECP, in the notice, had said that under the Political Parties Order of 2002, a disqualified lawmaker cannot hold any office in a political party.
The notification had also referred to the Supreme Court order on the Panamagate case, in which Sharif was formally asked to step down as prime minister.
The ECP had additionally observed that Article 15 of the PML-N's Constitution says that if the seat of party president is vacant, it has to be filled within one week's time.
The election body had asked the PML-N to elect a new party leader and then inform it.