Seizing on Oza's claims, AAP leader and Delhi Chief Minister Arvind Kejriwal tweeted, "If it is true, it reveals real face of BJP-Modi-Shah".
The allegations were denied by the BJP
In a letter to Kejriwal on July 4, Oza claimed that he was also present at the meeting which he said was held "in the wee hours at Shah's residence on September 15, 2015."
However, he did not clarify the place where the purported meeting took place.
Oza claimed that it was decided in the meeting that "Owaisi will spew poisonous communal speech, the script of which shall be written by Amit Shah."
Oza also claimed that newly-elected Gujarat BJP president Vijay Rupani is an "old friend" of Owaisi.
Oza claimed he was with Rupani when the latter met Owaisi "with great warmth" at Delhi Airport on March 11, as they were supposed to board the same flight.
In the high-stake Bihar election, the JD(U)-RJD-Congress alliance secured 178 seats in the 243-member state Assembly whereas the BJP-led NDA could bag only 58 seats.
Speaking to media persons, Oza, a lawyer at Gujarat High Court, said, "I was present in the said meeting. A detailed discussion took place and it was agreed that Owaisi shall field his candidates in Bihar, particularly in Muslim belt that was to go to polls on November 5 (last phase).
"It was decided in the meeting that Owaisi will vomit poisonous communal speech, the script of which shall be written by Amit Shah, which may have the potentiality to create communal divide in the society," the letter said.
"Many reputed and good people from different walks of life want to join AAP, but are waiting for a proper opportunity," said Oza who held a meeting with Kejriwal in Rajkot on Saturday and discussed his plans of joining AAP.