"There is a very small percentage of corrupt officials. There are professional complainants, who together are trying to ensure that the permissions are given in a particular way or are subverted," Mr Mehta told news agency PTI in an interview.
"We are now looking into this issue. We will break the back of this officials-activists nexus," Mr Mehta said, speaking in the aftermath of the Kamala Mills compound pub fire that claimed 14 lives last week.
"We will keep taking action till we break their backs," the senior IAS officer said, referring to the slew of demolitions of illegal constructions and alterations at over 350 establishments in the city as the Brihanmumbai Municipal Corporation (BMC) continued to raze these structures at hotels and restaurants, after the blaze.
"Just like in the nallah and road repair scam, where we found out who is the corrupt contractor, and who is the corrupt engineer and broke their backs, we will do the same here," Mr Mehta said.
"In the long term, we are looking at breaking the fire brigade into two parts, wherein the fire fighting wing is separate and the fire permissions and compliance wing is separate," he said.
The officer handling the issue of fire compliance will report directly to the ward officer, Mr Mehta said. Technically however, he will report to the chief fire officer, he added.
Asked if the political masters (Shiv Sena and BJP) have been supportive of the latest demolition drive, Mehta said "As far as the political will is concerned, the law is very clear. As bureaucrats, we are supposed to follow the law."
"Fortunately, in BMC and Mumbai, on the political side, we do not have a problem. The problem is with these professional complainants, who are not answerable to anyone," he said.
Asked if the professional complainants he is referring to included RTI activists, Mr Mehta said "We want to find out and act against people who misuse the law, whether it is RTI activists or any other people."
"RTI Act was always an instrument for people's good and I believe that it is one of the best things that could have happened. But yes, there are people who misuse the law.
And this is what I call a professional complainant," he said.
"However, they put up the front of being very concerned about citizens," the civic chief said.
Mr Mehta said the time has also come for citizens to impose some self discipline.
"That is equally important. You can't always say that you will keep doing what is wrong provided it maximises your profit or enjoyment," he said.
Asked about what caused the fire, Mr Mehta said "We should await the probe report."