The Chief Minister had gone to the Kolkata Book Fair on Wednesday evening. As she was leaving the venue, Ms Banerjee shouted at the guards saying, "Apnakay chabkano uchit" which in English means, "you should be whipped."
She said this not once but twice at least and so loudly, her audio is clearly captured on camera.
The police official who was the target of her anger is Kusum Kumar Dwivedi who has been her personal security for many years.
Ms Banerjee's outburst comes on a day when news headlines were dominated by former chief minister Buddhadeb Bhattacharjee's statement in an interview to a Bengali news channel that he did not believe that Mamata Banerjee was honest.
Mr Bhattacharjee said the financial condition of Mamata Banerjee's relatives had changed dramatically after she came to power.
He also said he could only give Mamata a zero when asked to rate his successor's performance.
In response, a senior minister of the Mamata Banerjee government, Firhad Hakim, held a press conference slamming Mr Bhattacharjee. He said Mr Bhattacharjee had lost the trust of the people and even his own constituency. (Read: Notice to Buddhadeb for questioning Mamata's honesty)
"We are sure he will finally apologise to Mamata for questioning her honesty," Mr Hakim said.
Earlier, the West Bengal Chief Minister got into another controversy after her comment on Prime Minister Manmohan Singh. "I personally met the Prime Minister at least 10 times. What else can I do? Shall I go beat him up? Then people will call me a 'goonda'. Anyway, they call me that. But I don't care. I can go to the very last for the people," she had said at a rally last month while criticising the Central government for hike in fertiliser prices.
Ms Banerjee later denied saying anything about beating up the Prime Minister and blamed the media for "distorting facts".
The comment was widely criticised with the Congress demanding an apology from her for using "undemocratic language to hurt the Prime Minister".
Election Results for Lok Sabha Election 2019 will be out on May 23. Get the latest election news and live updates on ndtv.com/elections. Catch all the action on NDTV Live. Like us on Facebook or follow us on Twitter and Instagram for news updates from each of the 543 parliamentary seats for the election 2019