Joshi claimed he had received fresh threat calls on his mobile phone from three different numbers and also through letters.
He had written the letter to Chidambaram on June 14, a week after he was forced to resign from the BJP. It was circulated to the media by Joshi's aides today.
"Again some people have started making fresh threatening call to me on my mobile...I have also received a hand written letter from a person Rasool Khan wherein I have been warned that I should get ready for my death," Joshi said.
He said he had received threat calls earlier and the government had provided him security after which he considered himself to be "a little bit safer in Delhi."
"...But I cannot manage my work and responsibility by sitting in Delhi. I want that these persons should be tracked down and suitable action taken against them as well as the persons behind their activity," Joshi said.
"I further pray for increasing my security cover not only in Delhi but also outside Delhi. Kindly do the needful and protect my life," he added.