He said that he will not attend the event marking the restoration of democracy, which "is suffering due to the fully and unconditional surrender of our country to the IMF by the government".
"So long as our people, who for months have been sending a resounding message from all the squares of the cities, is muzzled and remains in the margins, this celebration has no meaning or content," Tsipras said in his letter.
Greece's democracy "is not celebrating this year", Tsipras said, adding: "It is suffering due to the full and unconditional surrender of our country, by the government, to the International Monetary Fund, causing poverty, unemployment and desperation to the majority of our fellow citizens. It is hurting from the forceful blows resulting from the methodisations that circumvent the popular authority and set in motion painful developments, in absentia of the people. It is in tears due to the 3,000 teargas grenades that the police forces threw on June 29 against peaceful demonstrators, causing irreparable harm to our fellow citizens."
Tsipras ended his letter with the hope that "this is the first and last time that my conscience dictates such a decision" and that "democracy will not be the first victim of this horrendous crisis our country and people are going through".