Sinha stated in his letter that former telecom minister A Raja had earlier written to JPC chairman PC Chacko that the prime minister and prime minister's office (PMO) were aware of the decisions in the 2G spectrum allocation.
"He (Raja) has, therefore, dismissed the theory of the draft report of the JPC that he misled you (Singh)," Sinha said.
He also named parts of the draft report saying that the prime minister's cabinet colleagues had disapproved of the stand taken by him.
"Is it not time, Mr Prime Minister, you speak on these issues by appearing before the JPC? Your silence will confirm the worst fear of the people of India that you are fully involved in the 2G scam and if Sri Raja is guilty, so are you," Sinha said.
This is the third letter Sinha has written to the prime minister asking him to appear before the panel.