There was no immediate reaction from the Delhi government or the AAP.
A senior leader of the BJP-led North Delhi Municipal Corporation on Wednesday claimed that "legal notices" have been sent to Delhi minister Satyendar Jain and three other senior AAP leaders for levelling "false allegations" against the civic body.
NDMC Standing Committee chairman Chhail Bihari Goswami said the "defamation notice was sent today" to Mr Jain, Raghav Chadha, Atishi and Saurabh Bhardwaj.
There was no immediate reaction from the Delhi government or the AAP.
The AAP had earlier alleged "misappropriation of Rs 2,500 cr" by the NDMC in connection with the South Delhi Municipal Corporation. On Saturday, it had demanded a CBI inquiry into the alleged irregularity.
Mr Goswami, in a statement on Wednesday, alleged that "Aam Aadmi Party leaders are trying to spoil the image of North Delhi Municipal Corporation by making false statements".
"In view of which, he has sent a legal notice of defamation against these Aam Aadmi Party leaders," he said.
At a press conference on Saturday, Ms Atishi had claimed that the NDMC had waived about Rs 2,500 crore owed to it by the SDMC for its office at Civic Centre, which is in NDMC area.
The SDMC headquarters is housed in the Civic Centre building, also headquarters of the NDMC, post trifurcation of the erstwhile unified MCD in 2012. The EDMC headquarters is located in Patparganj in east Delhi.
The NDMC on Wednesday also issued a statement, saying it "outrightly denies the allegation of any misappropriation on account of waiving of the ground rent purportedly to be paid by the SDMC to the NDMC", and claimed "there is no truth in AAP's allegation".
The NDMC further said the municipal commissioner in its revised budget estimate 2020-21 and budget estimate 2021-22 held on December 8 "had not proposed or shown any income under the relevant head" on account of this subject.
"It would not be out of context to mention here that even in the last revised budget estimate (RBE) 2019-20 and budget estimate (BE) 2020-21 proposed by the commissioner, no dues pertaining to the ground rent or licence fee from the SDMC towards the Civic Centre occupation were incorporated," the NDMC claimed.
"However, the standing committee and the corporation have subsequently, on its own accord, after deliberation incorporated an amount of Rs 1815.77 cr in the RBE 2019-20 and Rs 320.00 cr in BE 2020-21, as expected income on account of ground rent or licence fee from SDMC towards the Civic Centre occupation," the statement said.
The RBE 2020-21 and BE 2021-22, as proposed by the commissioner of NDMC, are yet to be deliberated upon and passed by the standing committee and the corporation's house, it added.
"It appears that this amount of Rs 1,815 cr of RBE 2019-20, and Rs 320 cr in the BE 2020-21, plus the presumptive amount of Rs 320 cr in the BE 2021-22 has been clubbed together to arrive at a notional figure of Rs 2,457 cr," the NDMC claimed.