Bollywood and Mumbai are intertwined, each inconceivable without the other. But if local politicians keep verbally assaulting actors and film crews and attacking cinema halls, the industry could move out of the city.
This threat comes in the year that the industry is celebrating its 100th anniversary. Ramesh Sippy, the head of the Film and Television Producers Guild, warned Prithviraj Chavan, the Maharashtra state chief minister, that if the violence by local political groups were to continue, the industry will start looking for a safer city.
"It's going from bad to worse," said Sippy, the director of the 1970s film Sholay. "It's no fun if you are always looking over your shoulder wondering when the next attack will be. I don't want people's bones broken or their lives endangered. We must find an answer."
The threat to abandon Mumbai came after a series of attacks and intimidation by the Maharashtra Navnirman Sena (MNS), an offshoot of the right-wing nationalist Shiv Sena party.
The organisations glorify Maharashtrian culture and the local language, Marathi, with members spewing hatred against Muslims and seeking to stop people from outside the state coming to live and work in Mumbai in order to keep it "pure".
When it comes to Bollywood films, MNS leaders routinely demand that a film they do not like be withdrawn, using the threat of violence. If an actor or director makes a remark they disagree with, they come out on to the streets to burn his effigy.
"The moment they want a bit of media coverage, they attack the industry," said the film director Mahesh Bhatt. "It's the quickest and most effective way of grabbing the headlines."
The event that triggered Sippy's warning came on July 30, which is when MSN supporters vandalised 15 cars belonging to film stars and crew on his film set and smashed the vanity van of the well-known heartthrob John Abraham.
"If we are not given the security we need, we will have no choice but to make the painful decision to move out of Mumbai to another city," Sippy said. "It's not what we want, but we have to be able to work in safety."
On August 13, the MNS ordered multiplex owners to continue showing the Marathi film Bharatiya even though the owners wanted to replace it with the new release Ek Tha Tiger starring Salman Khan. Though it meant losing money, the owners bowed to the pressure.
"The violence and intimidation has been getting worse because the government doesn't send out a clear, unequivocal message that it won't tolerate it," said Komal Nahta, the editor of Film Information magazine. "It keeps sweeping things under the carpet. The government has to get tough."
The violence is particularly deplorable, said Nahta, because throughout its history the industry has managed to avoid sectarian and political divisions.
"It's always been secular and nonsectarian and now these groups are politicising everything," he said.
In a meeting with the authorities, top Bollywood figures demanded better police protection and more stringent action against the culprits.
Sensing an opportunity, the neighbouring state of Gujarat has already offered itself as an alternative location. The offer is understandable, as its film industry is huge. It churns out 1,000 films a year, employs some 2.5 million people and is worth US$3 billion (Dh11bn).
For most fans, though, the idea that their favourite stars would be anywhere but Mumbai is preposterous. The film industry's identity is totally fused with the city. Bollywood stars lend their glamour to the city, while the city lends its natural beauty - the Arabian Sea and British colonial architecture - to the industry. Anisa Sharma, a Bollywood fan living in New Delhi, simply can't see it happening.
"Gujarat? Perish the thought. That's like Hollywood moving to Buffalo. No offence to Buffalo, but it's a non-starter."
• On August 13, MNS activists warned all multiplex owners to continue showing a Marathi film at prime time even though its run was over and it was time to show the new release, Ek Tha Tiger, starring Salman Khan and Katrina Kaif. The owners bowed to the pressure.
• On July 30, a violent gang armed with iron rods and stones attacked Ramesh Sippy's film set, damaged a vanity van and vandalised 20 cars.
• The Shiv Sena warned the film industry in February against hiring Pakistani actors or dancers, saying it would "teach a lesson" to anyone who did so.
• In 2010, MNS gangs went on the rampage against Shah Rukh Khan and burnt his effigy after he questioned why Pakistani players were not being allowed to play in the Indian Premier League cricket tournament and passed the remark that "Mumbai is for all Indians".
• The filmmaker Karan Johar was attacked for letting his cast use the word "Bombay" in his 2009 film Wake Up Sid instead of the Indianised "Mumbai". Johar was able to release the film only after apologising to the MNS chief Raj Thackeray.
• In 2000, the Shiv Sena led violent protests against director Deepa Mehta's film Water for depicting Hindu society's treatment of widows.