Addressing a gathering of tens of thousands of his followers at Jinnah Avenue in the heart of Islamabad, Qadri claimed President Asif Ali Zardari, Prime Minister Raja Pervez Ashraf and the federal ministers could no longer hold office.
"End your government. I give you time till the morning to dissolve the National Assembly and provincial assemblies, otherwise people will make the decisions tomorrow," Qadri thundered to loud cheers from his supporters.
"Your mandate has ended, the fake mandate you obtained through wealth, rigging and fake votes. The people who gave you a mandate through the vote have taken back their mandate as a protest."
"Your government and assemblies have ended tonight," he claimed while speaking from a bulletproof cabin set up onmj a stage.
Qadri yesterday began a "long march" from Lahore to pressure the government to carry out sweeping electoral reforms, including the dissolution of the Election Commission and the formation of a caretaker set-up after consultations with the army and judiciary.
"The long march has ended at 2am this morning in Islamabad and now the revolution has begun," he said.
Though Qadri's Tehrik Minhaj-ul-Quran party had signed an agreement with the Islamabad administration to hold a peaceful protest a few kilometres from the National Assembly, the cleric surprised authorities by inciting his followers to remove barricades and move towards a square near parliament.
Qadri also incited policemen and paramilitary personnel to defy their officers, saying the officials would be removed by tomorrow.
He said the government would have time till 11 am, when he would deliver an address, to act on his demands.
The cleric's supporters removed containers placed on Jinnah Avenue and began moving towards the Red Zone that is home to the parliament, key government buildings and the diplomatic enclave.
After discussions with Tehrik Minhaj-ul-Quran officials, authorities announced at 4.30 am that the protestors would be allowed to gather at the square near parliament.
Qadri claimed four million people had joined his march but Geo News channel quoted official sources as saying that only 35,000 to 50,000 people had joined the protest.
The government had earlier mobilised some 10,000 personnel in Islamabad for the protest and more security forces, including troops of the Pakistan Rangers, were brought in early this morning.
TV news channels reported the army had also been called in to beef up security but this could not be independently confirmed.
Pakistan's political circles have been surprised by the sudden re-emergence of Qadri, a Canadian national who has lived outside the country for the past seven years.
A fringe player in Pakistani politics who was involved in several controversies in the past, Qadri returned from abroad last month after his party ran a multi-million rupee advertisement campaign in newspapers and on television.
Qadri subsequently addressed a large gathering at the Minar-e-Pakistan in Lahore on December 24 and gave the government time till January 10 to carry out electoral reforms.
At the time, he had warned he would march to Islamabad with his followers on January 14 and stage a sit-in till his demands were met.
The ruling Pakistan People's Party, main opposition PML-N and other major parties have accused Qadri of acting a front for the security establishment and foreign elements to delay the general election scheduled to be held by May so that the term of an interim administration can be prolonged.