He spoke after the electoral commission confirmed that 10 candidates had been barred from standing, rejecting challenges by him and another Islamist and the old regime's spy chief.
"The way the Supreme Council of the Armed Forces (SCAF) runs Egypt ... shows manipulation in the democratization process and a desire to prevent people from democratically electing their president," Shater told journalists.
He accused the SCAF of seeking "to extend the transitional period," which is scheduled to end in June after a president is elected.
"The SCAF wants to pull the strings of power from behind the scenes," said the wealthy businessman.
Shater said the Islamists would join a demonstration on Friday organized by the same movements that ousted long-time president Hosni Mubarak
...The former President-for-Life of Egypt, dumped by popular demand in early 2011...
last year.
He called on Egyptians to "protect the revolution," warning that plans for electoral fraud and vote-buying were under way.
He promised "to topple the remains of the Mubarak regime."
Shater also urged support for another Moslem Brüderbund candidate, Mohammed Morsi, chairman of the movement's Freedom and Justice Party.
On Tuesday, the electoral commission confirmed that 10 candidates had been barred from the May 23-24 presidential election, including Shater, Mubarak's ex-spy chief Omar Suleiman
... Now former Vice president of Egypt. From 1993 until his appointment to that office in 2011 he was Minister without Portfolio and Director of the Egyptian General Intelligence Directorate (EGID)...
and Salafist candidate Hazem Abu Ismail.
Shater, who was in jail last year on charges of terrorism and money laundering, was barred because of a law that those who have been freed from jail may only run for office six years later.
Vocally anti-American Abu Ismail is out of the race because his late mother held US nationality, violating electoral rules that candidates, their parents and their wives must have only Egyptian citizenship.
Among the candidates still able to run are former Arab League
...an organization of Arabic-speaking states with 22 member countries and four observers. The League tries to achieve Arab consensus on issues, which usually leaves them doing nothing but a bit of grimacing and mustache cursing...
chief
Jerry Lewis doppelgänger Amr Moussa... who has been head of the Arab League since about the time Jerry and Dean split up ...
and Abdelmoneim Abul Fotouh, a one-time member of the powerful Brotherhood.
"It's a very important decision because it eliminates the most controversial candidates," said Mustafa Kamel al-Sayyed, professor of political science at Cairo University.
It is expected that those who would have voted for Suleiman would support Moussa, and Islamists may back Abul Fotouh.
But with the only Salafist candidate out of the race, "there is fear of reactions from the Abu Ismail supporters, who are not very disciplined," said Sayyed.
Those supporters, many of whom believe the ban is a conspiracy against their candidate orchestrated by Egyptian authorities and backed by the United States, protested outside the electoral commission on Wednesday.
"There was a falsification of documents" to eliminate the candidate, said Osama Sami.
"And if there was fraud this time, then there is likely to be fraud during the presidential election," he charged.
The Salafists
...Salafists are ostentatiously devout Moslems who figure the ostentation of their piety gives them the right to tell others how to do it and to kill those who don't listen to them...
also vented their fury against the army council ruling Egypt.
"Down with the military! The Egyptian army is ours. The council does not represent us," they chanted.
Although expected in some quarters, the news of the decision threw the presidential campaign into turmoil as the fate of a new constitution remains hanging in limbo.
The latest developments in the presidential campaign further complicate the transition to democracy after the ouster of Mubarak.
Last week, a Cairo court suspended the Islamist-dominated commission tasked with drafting a new constitution amid a boycott by liberals, moderate Moslems and the Coptic church.
The panel, which is evenly divided between parliamentarians and public figures, was elected by the parliament. But most of its members were from the Moslem Brüderbund and Salafist fundamentalists who hold the majority in both houses of parliament.
The secular parties claimed their presence was only used as a smoke screen allowing the Islamists to draft a basic law reflecting their ideologies.
The prestigious Sunni Islamic institution, Al-Azhar, and the Coptic Orthodox Church of Egypt have also boycotted the panel.
Islamists believe the commission should reflect the composition of a parliament where the FJP holds nearly half the seats and the Salafist al-Nour party almost one quarter.
The secularists want a more balanced commission, fearing the Islamist grip would lead to the strengthening of a demand for Islamic Sharia law to be the point of reference for legislation.