He alleged that the Devendra Fadnavis-led government was suppressing the freedom of speech.
The seminar had been organised in the wake of controversy over BJP-Shiv Sena government's decision to give 'Maharashtra Bhushan' award to the historian Babasaheb Purandare.
Purandare's detractors alleged that he falsely portrayed Shivaji as anti-Muslim.
Former Supreme Court judge Justice P B Sawant, writer A H Salunkhe, senior journalist Dyanesh Maharao, social activist Srimant Kokate and NCP legislator Jitendra Awhad were to speak at the seminar.
Such things were the signs of "emergency" as apprehended by veteran BJP leader L K Advani, he said, adding that the progressive people in the state will not allow the government to "fulfil its agenda".
In a tweet, Jitendra Awhad termed the denial of permission for the seminar as "fascism" and "murder of democracy".
