Dobrowolny said in an email Monday that he is talking with his legal staff and didn't immediately have a specific comment about the letter.
"As a general principle, we believe that a new company providing value to people should be regulated and not banned," Dobrowolny wrote. "This applies also to companies like Airbnb, Uber and Lyft that are continuously facing difficulties while delivering something that makes users happy. Regulation is fundamental in driving innovation, while banning is just stopping it."
The city attorney's warning to Monkey comes about a month after his office started investigating the startup, which began its San Francisco operations in April.
"Technology has given rise to many laudable innovations in how we live and work and Monkey Parking is not one of them. It's illegal, it puts drivers on the hook for $300 fines, and it creates a predatory private market for public parking spaces that San Franciscans will not tolerate," Herrera said in a written statement. "People are free to rent out their own private driveways and garage spaces should they choose to do so. But we will not abide businesses that hold hostage on-street public parking spots for their own private profit."
Parking in San Francisco has long been known as a driver's worst nightmare. A recent San Francisco Municipal Transportation Agency parking census reported that the city has 440,000 parking spots available but only 275,000 of those are street parking.
Herrera's letter to Monkey also asked tech giant Apple to immediately remove Monkey's application from its app store.
Two other tech companies Sweetch and ParkModo, parking apps that Herrera said also violate city and state law will receive similar cease-and-desist warnings later this week.