Opposition parties in Tamil Nadu on Thursday criticised the government’s decision to transfer a senior officer of the Crime Investigation Department, which is investigating the case of a college professor accused of luring students to sex work.

The Dravida Munntera Kazhagam and the Pattali Makkal Katchi said the government had rushed its decision to transfer Additional Director General of Police K Jayanth Murali immediately after handing over the case to the Crime Branch-Crime Investigation Department. Murali was transferred to the Vigilance and Anti-Corruption wing. Amaresh Pujari, the assistant director general of police (crime), will replace him.

The DMK and the PMK demanded an inquiry by the Central Bureau of Investigation. The episode has brought disrepute to Tamil Nadu, DMK Working President MK Stalin told PTI.

“Who are involved in this case and who are behind it?” Stalin asked. “If this has to be ascertained, and for the truth to emerge, the probe has to be done by the CBI under the supervision of the High Court.”

PMK chief S Ramadoss said there was a conspiracy to bury the case. He said that the government’s decision was shocking. “All the bigwigs in the sexual scandal can be exposed only by a CBI probe and this is essential for the parents in Tamil Nadu to send their children to schools and colleges without fear,” he said.

Nirmala Devi, who was arrested on Tuesday, is accused of luring female students of Devanga Arts College in Virudhunagar district for sex work. In an audio clip that was leaked online on Sunday, Devi is heard telling the students of an “opportunity” to do “certain things” for senior officials of the university.

“For doing something successfully, they [the officials] are expecting college students for certain things,” she is heard saying in the audio clip. “I believe, being college students, you understand what they expect. If you accept this scheme, MKU [Madurai Kamaraj University] will be your backbone.” Devi has accepted that it is her voice in the audio clip. However, she claimed that the students had misinterpreted her.

The case attracted more attention after Devi claimed that she knew Governor Banwarilal Purohit, who is also the chancellor of the Madurai Kamaraj University. Purohit on Tuesday denied any link to the professor. He claimed that he had never even seen the professor, and promised that strict action would be taken against the guilty.