Nawaz Sharif was released from prison last month pending an appeal.
A NAB prosecutor told the judge that Shehbaz had "misused his powers" as chief minister of Punjab province and granted the contract to a favorite company, causing "losses of millions of rupees to the national exchequer".
The meeting being held in Model Town, Lahore is being attended by the party's CEC members.
However, Sharif's counsel, Azam Nazir Tarar said his client was remanded in custody for 10 days to be interrogated. His daughter Maryam was awarded seven years and Capt Safdar one year sentence for abetment.
Both were arrested at Lahore airport upon their arrival in Lahore from London.
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The PM, while responding to the allegations leveled against him that the arrest of Shahbaz Sharif was a kind of political victimisation, said NAB (National Accountability Bureau) was not under his command, it is an independent organisation, and it was also summoning him in a case, he added. "Such actions will no more be tolerated". Their party, along with all other major Opposition parties, denounced the polls as rigged, alleging the military and courts of tipping the scale in favour of Mr. Khan's party.
Malik Mohammad Ahmed, a spokesman for Sharif, said their leader was not involved in any wrongdoing.
PML-N leader and Shahbaz's son, Hamza Shahbaz Sharif, lashed out at the Pakistan Tehreek-i-Insaf government over his father's arrest, claiming that it was part of Imran Khan's effort to save his government after the October 14 by-elections.
In court, Shahbaz's counsel Amjad Pervez seemed to justify the former Punjab CM's cancellation of the said contract. They informed the speaker that a requisition for convening the session had already been submitted to the NA Secretariat. NAB will request a 14-day remand of Shahbaz, NAB prosecutor Waris Ali Janjua told DawnNewsTV. "This arrest which took place close to the by-elections shows that the government is scared of the PML-N".
"They can not arrest the leader of the opposition in this manner", the lawyer said. "The NAB will produce the former Chief Minister of Punjab in the honourable accountability court tomorrow", a statement from the agency said.