Accompanied by Delhi Congress chief Ajay Maken and other party leaders, Kumar, a three time MLA from Bawana, filed his nomination at the DC office in Narela.
"The Congress has fielded an honest worker as the candidate for the Bawana by-election who has served the constituency selflessly for 15 years, faithfully upholding the values, policies and programmes of the party," Maken said.
The last date for filing nomination papers is August 5. Voting will be held on August 23 and the polled votes will be counted on August 28, as per the scheduled announced by the Election Commission.
Later, Prakash joined the BJP and was fielded as the party candidate in the bypoll.
Kumar who was elected three times in a row from Bawana, between 1998 and 2008, is presently the district president of the Congress.
The Aam Aadmi Party (AAP) has named Ramchandra as its candidate in the bypoll.