The two leaders' departure comes at a time when the Congress is struggling to keep its house in order to save the 13-month-old Congress-Janata Dal-Secular government in Karnataka following the resignation of 11 MLAs on Saturday.
Rahul Gandhi's stepping down has already triggered a wave of protests and resignations by party functionaries from across the country. The Congress on June 19 dissolved the Karnataka Congress Committee sparing state President Dinesh Gundurao and Working President Eshwar Khandare.
The party has also dissolved all the district Congress committees in Uttar Pradesh and in June formed a three-member Disciplinary Committee to look into the complaints of gross indiscipline and anti-party activities.
On Sunday, Scindia, who was made the western Uttar Pradesh in-charge ahead of the Lok Sabha polls, tweeted: "Accepting the people's verdict and taking accountability, I have submitted my resignation as General Secretary of AICC (All India Congress Committee) to Rahul Gandhi. I thank him for entrusting me with this responsibility and for giving me the opportunity to serve our party."
He was in-charge of 39 out of 80 parliamentary seats in Uttar Pradesh, while Priyanka Gandhi Vadra was made in-charge of 41 seats in eastern Uttar Pradesh.
However, the party could manage to win only one seat Rae Bareli represented by UPA chairperson Sonia Gandhi in the state.
In a major embarrassment, outgoing party President Rahul Gandhi lost his family turf of Amethi to Union Minister and Bharatiya Janata Party (BJP) leader Smriti Irani by a margin of 55,000 votes.
Earlier in the day, Deora quit as the Congress' Mumbai chief, barely three months before the crucial Maharashtra Assembly elections.
He has recommended a provisional set up of a collective leadership of three senior leaders to oversee the city unit until the upcoming polls.
Deora is likely to move to New Delhi for a national role in the Congress, party sources said.
According to an aide, Deora had expressed his desire to quit shortly after meeting Rahul Gandhi in New Delhi on June 26.
His move is seen as "an expression of solidarity and collective responsibility with outgoing Congress President Gandhi's resignation".
Deora, a former Union Minister, was appointed President of Mumbai Congress on the eve of 2019 Lok Sabha elections, replacing Sanjay Nirupam.
The time that he was given to prepare for the elections was too little and too late, said the aide.
Nevertheless, during his brief tenure, he united the rank and file of the party and put an end to identity politicsin Mumbai Congress in the hope that the party once again returns to its multilingual, multicultural and socio-economically inclusive ideals.
The party, under his leadership, gave a decisive fight to the BJP-Shiv Sena combine in Mumbai, the statement said.
"In spite of many constraints, including his own election campaign, Deora was able to support Lok Sabha candidates to put up a strong fight."
Deora reiterated that he was "always available to serve the party as a trusted and resourceful lieutenant and looks forward to playing a more important role nationally".
He added that political realities have changed since 2019 results and all have to get ready for roles that these times demand.
( With inputs from IANS )