In 2015, Thakur had registered a police complaint against Mulayam Singh, alleging that the then Samajwadi Party chief threatened him with dire consequences if he does not mend his ways.
Thakur had also released an audio tape purportedly containing the voice of the former SP chief.
He was suspended on July 13, 2015, days after his allegations against Mulayam.
The suspension with immediate effect came on a day when Thakur approached the Union Home Ministry in Delhi seeking a CBI probe into the rape case filed against him after he lodged a complaint against Mulayam for threatening him.
The state government had then initiated a vigilance inquiry against him. However, the Lucknow bench of the Central Administrative Tribunal had stayed the suspension of Thakur in April and ordered his reinstatement with full salary with effect from October 11, 2015.
He had also requested the Centre to get the departmental inquiries against him transferred to some other state, alleging bias and irregularities on the part of the senior state government functionaries.
Thakur had said a "false" rape case had been slapped against him after he lodged a complaint against the ruling SP supremo in Lucknow on July 10 for threatening him. "I want a CBI investigation into the rape charge against me," he said.
Complaint filed by Amitabh Thakur against former UP chief secretary
Senior IPS officer Amitabh Thakur on Tuesday filed a complaint against former Uttar Pradesh Chief Secretary Alok Ranjan and Principal Secretary (Home) Debashish Panda, accusing them of forging documents relating to his suspension.
Thakur said that the Inspector of Hazratganj police station has assured him of appropriate action in the matter.
The complaint says Thakur's suspension was not renewed within 90 days' period and hence he requested to be reinstated from October 10, 2015.
"These officers colluded with each other to forge false documents regarding holding of Civil Service Board meeting on December 10, 2015 and March 11, 2016 without any such meeting actually taking place. They also created many false documents to extend my suspension," the police officer said in his complaint.
Amitabh Thakur, who crossed the path of then Akhilesh Yadav government for filing an FIR against Mulayam Singh Yadav for telephonically threatening him, says he has enough documentary evidence to prove his case against the two officials and was hence pressing for lodging an FIR.