Kapil Mishra is now hospitalised after he fainted during a press conference in which he revealed purported details of alleged financial irregularities committed by the Aam Aadmi Party for its donations.
He fainted midway and was admitted to hospital.
On May 7, Mishra accused Kejriwal of accepting bribe of Rs 2 crore from Delhi health minister Satyendra Jain in front of him.
Mishra alleged that the party concealed around Rs 36 crore from the party workers and the government.
'All these shell companies are registered in the name of AAP MLA Shivcharan Goel.
Providing details of donations over Rs 20,000 that were made to AAP, Mishra said the party actually received funds worth Rs 32.46 crore in 2014-15, not just the Rs 27.48 crore listed on AAP's website.
The former water resources and tourism minister in the Delhi government is suffering from "a little weakness and mild dehydration", an RML doctor said.
The rebel leader alleged that AAP routed unaccounted money into party coffers through shell companies, converting the black money into white.
Mishra was suspended from the party on May 8. Mishra has called himself as an eyewitness to that transaction. "Arvind Kejriwal, have some shame".
Meanwhile, Raghav Chadha - who along with Satyendra Jain, Ashish Khetan, Sanjay Singh and Durgesh Pathak - has been accused by Mishra of travelling overseas on ill-gotten wealth, reacted to the allegations by saying: "I think Kapil Mishra is mentally unstable..."
As he brandished some cheques before reporters, Mishra fainted and was taken to Ram Manohar Lohia Hospital here. Mishra said, adding that his next "expose" would be tomorrow. "I hv to go to CBI and CBDT. starting on liquids now", Kapil Mishra tweeted. "Inevitable", Sunita Kejriwal, a former income tax commissioner, said on Twitter.
Mr. Mishra's mother, Annapurna Mishra, had fired a salvo at Mr. Kejriwal last week, accusing him in an open letter of spreading "falsehood" against her son by saying he was associated with the BJP.