He sent his resignation letter to Congress president Sonia Gandhi.
In his letter shared with the media, the former chief minister alleged that he was forced to take this "tough decision" as some Congress leaders were conspiring against him ahead of the Assembly polls, expected to be held in Gujarat in December.
On July 21, Vaghela on his 77th birthday had announced to quit the Congress at a public gathering of his supporters.
Vaghela, who joined the Congress in 1998, claimed that just like some Congress leaders conspired against him in 2009, when he lost Godhara (Panchmahal) Lok Sabha seat, similar attempts were made to oust him from the party in recent times.
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Vaghela said since he has also decided to resign as the sitting Congress MLA of Kapadwanj seat, he will submit his resignation to the Gujarat Assembly speaker in the coming days.
In his 'farewell' speech on Friday, Vaghela announced he would resign as MLA on August 15, after the Rajya Sabha polls, to be held on August 8.
Venting his anger on the Congress, Vaghela claimed he was left with no other option but to resign as his suggestions for the upcoming Assembly polls were not accepted.
On Friday, the former RSS leader, who left the BJP 20 years ago and later joined the Congress, also announced that he will not join any political party, not even the BJP.
Though he refused to divulge details about his future plans, he maintained he is not retiring from public life.
Vaghela had been at loggerheads with the Congress leadership for quite some time over his demand that he be projected as the chief ministerial face in the poll-bound state.
Vaghela's move comes close on the heels of the Congress failing to muster its entire strength in the presidential election held on July 17.
Congress-backed candidate Meira Kumar could garner only 49 votes against the party's strength of 57 in the state assembly.