Nearly 10 months on from the last elections, the country still has no government, new prime minister or new president, due to repeated squabbles between factions over forming a coalition.
In the latest political turmoil to strike the oil-rich but war-scarred nation, Sadr called for a "revolutionary and peaceful process, then early democratic elections after a dissolution of parliament".
His televised speech came as calls for dialogue intensify after his supporters occupied parliament for a fifth consecutive day, in protest at a nomination for prime minister by a rival Shiite faction, the Iran-backef Coordination Framework.
However, parliament can only be dissolved by a majority vote, according to the constitution. Such a vote can take place at the request of a third of lawmakers, or by the prime minster with the president's agreement.
"I am certain that the majority of the population is exasperated by the ruling class in its entirety, including some (politicians) belonging to my movement", Sadr said.
"From now on there will be no more old-guard politicians, whatever their affiliation," he added.
Sadr's bloc emerged from elections in October as the biggest faction, but it was still far short of a majority.
In June, his 73 lawmakers quit, ostensibly in a bid to break the political logjam.
Sadr, who once led an anti-US militia and who has millions of devoted followers, noted also that he had "no interest" in negotiating with his rivals.

Risk of escalation
Along with their sit-in, the cleric's supporters have set up an encampment outside parliament with tents and food stalls, and Sadr on Wednesday called on them to continue.
"The revolutionaries and protesters participating in the sit-in must stay and continue their camp until the demands are realised," he said.
In multi-confessional and multi-ethnic Iraq, government formation has involved complex negotiations since a 2003 US-led invasion toppled dictator Saddam Hussein.
The resignation of Sadr's lawmakers led to the pro-Iran bloc becoming the largest in parliament, but still there was no agreement on new top posts.
The Sadrist camp was outraged by the Coordination Framework last week nominating former minister Mohammed Shia al-Sudani as prime minister.
The Coordination Framework is a grouping that includes former prime minister Nuri al-Maliki, a long-standing foe of Sadr, and the Hashed al-Shaabi, a former paramilitary network now integrated into the security forces.
Outgoing prime minister Mustafa al-Kadhemi has called for a "national dialogue" in a bid to bring all sides together to talk, and on Wednesday he spoke with President Barham Saleh.
Both men stressed the importance of "guaranteeing security and stability" in the country, according to the Iraqi News Agency.
Sadr's foe Maliki said late Wednesday "serious dialogue giving hope for resolving differences... begins with respect for constitutional inistitutions".
Thousands of Coordination Framework supporters have held counter-protests in Baghdad against the occupation of parliament.
"Don't believe the rumours that I don't want dialogue," Sadr said on Wednesday.
"But we have already tried and experienced dialogue with them," he added. "It has brought nothing to us and to the nation -- only ruin and corruption."
Earlier on Wednesday, the United Nations mission in Iraq called on leaders to "prioritise (the) national interest" and end the long-running power struggle.
"Meaningful dialogue among all Iraqi parties is now more urgent than ever, as recent events have demonstrated the rapid risk of escalation in this tense political climate," the UN mission warned.
French President Emmanuel Macron also spoke with political leaders on Wednesday, saying that "dialogue and consultation" was the only way out of the crisis.
Al-Monitor
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