Former Punjab chief minister Amarinder Singh on Tuesday resigned from the Congress and also christened his newly launched party as Punjab Lok Congress.
He sent a seven-page resignation letter to party president Sonia Gandhi, sources said.
Singh had quit as the Punjab chief minister in September amid a bitter power tussle with state Congress chief Navjot Sidhu.
A few days ago, Singh had dismissed reports of back channel talks with the Congress as incorrect , saying the time for rapprochement was over and his decision to leave the grand old party was final.
He has indicated that he will float a political party ahead of Assembly polls in Punjab.