Mr Sharif has accused President Zardari of being behind the ban
The Pakistani government has warned former Prime Minister Nawaz Sharif that he could face charges of sedition if his supporters turn to violence.
The warning came as lawyers and Sharif supporters plan "a long march" to Islamabad this week.
They will condemn a Supreme Court order banning Mr Sharif from holding public office and the failure to reinstate judges who have been sacked.
Mr Sharif has accused President Asif Ali Zardari of influencing his ban.
The president has denied the charge.
The protesters are demanding the restoration of former chief justice of the Supreme Court, Iftikhar Chaudhry, and other judges sacked by Pakistan's former military ruler, Pervez Musharraf.
At a televised news conference, Pakistan's top security chief, Rehman Malik, said peaceful protests would be allowed, but he read out extracts from Mr Sharif's speeches accusing him of calling on people to defy the government.
"Inciting people for disobedience is sedition," Mr Malik said. "It could get life imprisonment."
Mr Malik said the government had "no intention" of arresting Mr Sharif, but hinted it had grounds to do so, especially if violence broke out during the protest.
Mr Sharif told his supporters on Monday: "We cannot leave Pakistan at the mercy of [President] Zardari.
"People should rise and join the long march to Islamabad to save Pakistan."
"The emotion I am seeing here is a prelude to a revolution."
Correspondents say the court ruling banning Mr Sharif and his brother from elected office has plunged the country into political turmoil.
The crisis has been aggravated following the imposition of direct federal rule on Mr Sharif's powerbase, Punjab province.
Mr Sharif has said the Supreme Court is dominated by judges appointed during a state of emergency imposed by Mr Musharraf and that Mr Zardari twice broke promises to restore the original judiciary.