The 3D sci-fi thriller was produced by Vishesh Films, which is a company co-owned by Mahesh and Mukesh Bhatt.
"I will not pass the buck to the Fox marketing team. It's time we at Vishesh bravely take the debacle of 'Mr X' in stride move on!" Bhatt, 66, posted on twitter.
"BLAME ME: It is content & content alon which is responsible for a film's failure. Mr X bombed at the box office because of my content," he said.
The film was released in both 2D and 3D on April 17.
Actress-turned-director Pooja Bhatt lauded her father's candidness.
"That is why you are you and the rest of the industry is well, them! Salutations Mr Bhatt! You make me proud yet again!" Pooja tweeted.