The director has just screened the adaptation of the Salman Rushdie novel at the Film Festival of Kerala.
Photo gallery - the BFI Midnight's Children premiere:
Copyright: Rex Features Can NguyenShe told IANS: "There is nothing in the film that is not historically accurate. Otherwise, believe me, the censor board would have not been so generous.
"The film is not just about Mrs Gandhi. That is just an aspect of what happened. The emergency [the Indian Emergency imposed by Indira Gandhi from June 1975 to March 1977] is a reality, everyone knows about it. And I don't think she has been portrayed in any other way than accurate."
Mehta has been criticised for featuring a map of India at the end of the film without the contested regions Kashmir and Jammu.
"The map of India is a miss," the director said. "I did not know that, and I wish I had that when you show a map of India, you have to show Jammu and Kashmir.
"I had absolutely no idea, so I am going to do that immediately and I have absolutely no pain at all that it has to be done. So it is hardly controversial."
Midnight's Children secured an Indian distributor in October despite fears about its subject matter.
The film releases on Boxing Day in the UK.
Watch the trailer for Midnight's Children below: