“The tribunal ordered the dissolution of the NDP and the seizure of his money. Its headquarters and its buildings will be transferred to the government,” a source told Agence-France Presse.

The party dominated Egyptian politics since Mr. Mubarak’s predecessor, the late President Anwar el-Sadat, established it in 1978. Islamists assassinated Mr. Sadat in 1982, while he was reviewing a military march-past in Cairo. Mr. Mubarak, then his deputy, was on the same stand, and was injured in the violence.

The party’s headquarters were torched during the protests that forced Mubarak to step down, and its supporters were blamed for some acts of violence during the demonstrations.

Ahmed Ezz, a prominent businessman and the secretary for NDP’s organizational affairs, was detained following the departure of Mr. Mubarak.

Now Mr. Ezz is being held in detention at the Bora Farm prison in Cairo, where his fellow inmates include Mr. Mubarak’s sons, Gamal and Alaa.

They, like their father, are under arrest and are being questioned on corruption and other charges. The former president, who is reportedly suffering from a heart ailment, has been admitted to a military hospital in Cairo. He had earlier been living at a lavish home in the resort community of Sharm El Sheikh.

Mr. Ezz reportedly used his enormous wealth to promote his political career and climb high ranks in the ruling party using his connections with Gamal Mubarak, the head of the policies committee in the party.

He was widely blamed for the widespread fraud that marred parliamentary elections held in November and December 2010. The former ruling party won all but a small fraction of the chamber’s 518 seats. Mr. Ezz denied the charge in an interview with Al Arabiya TV.

In the interview, Mr. Ezz told Al Arabiya that it was difficult to predict NDP’s future but he said the party would likely remain politically active.

He acknowledged that the NDP did not expect demonstrations to escalate to a full-fledged uprising that could oust the regime.