The actor plays the only "negative" role in the film, which co-stars Tusshar Kapoor and Naseeruddin Shah as Silk Smitha's (Vidya Balan) lovers.
A source told DNA India: "This was supposed to be kept a secret but now it has leaked out that Emraan apparently plays Mahesh Bhatt, even though it is still unclear as to what relationship did he share with Silk Smitha.
"Emraan on his part did the research and read up on everything available on his uncle. He also hounded Bhatt to divulge information that was not known to people."
The character played by Bhatt embarks on a relationship with Smitha, despite his animosity towards her.
Silk Smitha was a South Indian actress famous for appearing scantily clad.
Bhatt recently denied that Balan is suffering from exhaustion because of the long hours on the set of The Dirty Picture.
The actress was recently hospitalised after her haemoglobin levels fell dramatically, forcing the shoot to be delayed.
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