Diamond merchant Mehul Choksi, co-accused in the Rs 13,540 crore Punjab National Bank (PNB) fraud, has said that "exaggerated" allegations by multiple investigating agencies has left him "completely defenceless" and that he feared for his safety to return home.

In a two-page March 16-dated letter to the Central Bureau of Investigation (CBI), Choksi denied he was a partner of Diamond R US, Stellar Diamond and Solar Exports.

These firms have been accused of conducting fraudulent transactions with Firestar International and Firestar Diamond International owned his nephew Nirav Modi, who is also an accused in the PNB fraud.

The companies were named by the CBI in an additional FIR filed on February 14. Choksi was summoned to appear before the CBI on March 16 for questioning in the case.

Reiterating that it was "impossible" for him to return to India, Choksi said his health condition was not conducive and that his passport remained suspended.

"Till date, the Regional Passport Office (in Mumbai) hasn't communicated with me and my passport remains suspended. I have the deepest respect for your offices and assure you that I am not making any excuse, whatsoever, to travel to India.

"I reiterate that I am abroad and have earlier also responded to your notices. Surprisingly, the issues raised remain unaddressed, making my fear of safety rise to extreme levels."

He questioned the CBI move to name him in another case related to the bank fraud "knowing fully well that I have no concern whatsoever" with Diamond R US, Stellar Diamond, Solar Exports.

"I am neither a partner (of these firms) nor do I have any kind of association with the three concerns."

He said various actions by multiple agencies taken against him and "the manner in which the allegations have been exaggerated has left me completely defenceless".

"In any case", he said, "I am extremely held up in my business abroad and am working hard to resolves the issues it is facing due to the unnecessary closure of business in India due to untenable allegation." Choksi had left the country along with his nephew and other family members in January this year.

He said doctors had advised him "not travel for a period of four to six months".

"I am unable to travel to India due to my persisting health condition. In February 2018, a cardiac procedure was conducted and medical follow ups still remain and as the entire procedure could not be completed. The situation still remains," he said.