Presidency University has lost yet another distinguished chair professor to the yawning pay disparity between the College Street institution and central universities.

Sajal Nag, Netaji Subhash Chandra Bose Distinguished Chair Professor in Social Sciences, had come on lien from Assam Central University in March. He will be heading back to the Silchar institute.

Nag, who was getting Rs 40,000 less than what he used to earn every month in Assam, cited ill health in his quit letter.

He, however, spoke his mind while talking to Metro. "In my appointment letter, I was promised that I would be given pay protection as much as possible. The university had written to the higher education department, asking it to implement what was promised to me. But nothing has been done over the past nine months. How long can one wait?" Nag said.

At Presidency, a distinguished university professor gets Rs 1.25 lakh a month. At Assam Central University, Nag's salary was around Rs 1.65 lakh.

The salary gap would widen further, Nag pointed out, once the Centre implements the pay commission's recommendation of a salary hike by at least 20 per cent.

Since 2013, the state government has been offering pay protection to academics coming from central institutes to state universities as vice-chancellors. Presidency VC Anuradha Lohia - who had come from Bose Institute, which functions under the Centre - enjoys the privilege.

The state, however, is yet to decide on granting pay protection to distinguished university professors at Presidency.

Nag is the second distinguished chair professor after Sabyasachi Bhattacharya to quit Presidency.

Bhattacharya, who was Acharya Jagadis Chandra Bose University Distinguished Professor in Natural Sciences, had quit nine months into his tenure and returned to the Tata Institute of Fundamental Research (TIFR), from where he had come on lien.

Bhattacharya, a highly regarded physicist and a Presidency alumnus, had cited lack of academic independence and plurality on the campus as the reasons that prompted him to leave.

However, he also pointed out that he was getting Rs 75,000 less every month compared to his salary at the TIFR.

When asked whether he would have stayed on had he been given "the pay protection to the extent possible", Nag said: "I would have given it a thought."

He added his health had played a part, too, in his decision-making. "I have not been keeping well. I suffered from typhoid two-three times. With my family in Silchar, I was finding it difficult to cope," he said.

Asked why Nag had to quit, Presidency University registrar Debojyoti Konar said: "Prof Nag has quit because of health issues. The pay disparity has nothing to do with his decision."

Swapan Chakravorty is the only distinguished chair professor still attached to Presidency. Amitabha Dasgupta, the first chair professor appointed by Presidency, did not join.