Only days after mysterious posters appeared in Delhi and Ahmedabad criticising his forced exit from the BJP national executive, Joshi sent a letter to party president Nitin Gadkari.
"Sanjay Joshi has requested Nitin Gadkari to relieve him from the party. The request has been accepted," BJP spokesman Prakash Javadekar said in a brief statement here.
Javadekar refused to go into reasons for Joshi's sudden move but said the resignation was sent Friday.
The otherwise media shy Joshi told journalists at his residence here that he had decided to leave the BJP "due to Modi".
An activist with the Rashtriya Swayamsewak Sangh (RSS), Joshi was seconded to the BJP in 1988 when the party was growing on the strength of the Ayodhya movement.
As his relations with Modi deteriorated, a sleaze CD apparently featuring Joshi forced him to leave the BJP in 2005.
Gadkari rehabilitated him, inducting him into the national executive and making him in charge of this year's Uttar Pradesh election campaign.
This upset Modi, who stayed away from a BJP leadership meet in October last year and the Uttar Pradesh campaign this year.
Gadkari had to eventually ask Modi to leave the national executive to placate the Gujarat chief minister and to ensure's his attendance in last month's BJP leadership meet in Mumbai.
The developments have caused divisions both within the BJP and RSS, with one section critical of the way Joshi had been treated and another saying that Modi had to be accommodated in view of the coming Gujarat elections.
In Gujarat, Joshi is looked upon with awe by those still in the BJP who are upset with Modi's style of functioning. Those who have left the party in the state also because of Modi are considered close to Joshi.