“As President of the Congress party, I am responsible for the loss of the 2019 election. Accountability is critical for the future growth of our party,” he said in a letter that was put on his Twitter account.
“It is for this reason that I have resigned as Congress President.”
The letter said: “Rebuilding the party requires hard decisions and numerous people will have to be made accountable for the failure of 2019.
“It would be unjust to hold others accountable but ignore my own responsibility as President of the party.”
Gandhi said that while it was important for someone new to lead the Congress, “it would not be correct for me to select that person”.
Earlier in the day, Gandhi told reporters in Parliament: “I have already submitted my resignation and I am no longer the party chief.
“The Congress Working Committee should convene a meeting at the earliest and decide on a new party chief.”
Gandhi offered to resign after the Congress won just 52 of the 542 Lok Sabha seats.