Enforcement Directorate Joint Director Rajeshwar Singh has shot off a scathing letter to Revenue Secretary Hansmukh Adhia, asking him why he has developed "animosity" against him by "siding with scamsters and their affiliates".

The letter dated June 11, which was sent through ED Director Karnal Singh, came in public domain on Wednesday as the Supreme Court said the government was free to investigate allegations against him, which included his suspected links with an Indian with alleged ISI connections. The ED issued a statement to rebut the claims in a report submitted by the Centre in SC.

In his letter, Singh said his performance was rated "outstanding" in the past 20 years but "why do you disregard their opinion? Is it possible for me to have managed all of them over a period of time". He said his promotion in the grade of Additional Director in the ED was due from April 1, 2017, but it has been more than seven months and there has been "absolutely" no progress.

"Am I being targeted because I do not appear to be submissive and speak my mind on all issues assigned to me," he said.

"I am astutely aware that this is being done to not just humiliate me but also to ensure that the investigation in certain crucial cases I handle, ought to derail. May I beg to ask if you are compromising on larger aspects of our national interest to set scores on an ego trip that is absolutely uncontested from my side," he said.

He said former finance minister P Chidambaram made his "life an accentuated hell" as he was investigating him and his son Karti. Chidambaram "sported an open and direct grudge against me" because of Supreme Court monitored Aircel-Maxis investigation, he said.

"However, what thoroughly baffles the undersigned, is the animosity you have fashioned against me by siding with scamsters and their affiliates in a sustained manner. It has become more than difficult for me to survive this continued onslaught and persistent vilification from all the quarters for doing my job," he said.

Singh also sought to corner Adhia saying, it pained him further that he has expressed many a time to senior officers over casual conversations that "I have been manipulating the judiciary, especially the Supreme Court of India".

"It is strange and also unbelievable that after so many years in public service, you believe that so many judges can be manipulated and that too over such a long period of time," he said adding he had sought a personal meeting from him for explaining his side but was not granted.