Soon after counting began, Shashi Tharoor's team alleged that there were several "issues".
Shashi Tharoor today alleged "extremely serious irregularities" as votes were counted two days after the Congress held a milestone election, the first in over 20 years, and one in which no Gandhi was in the race. Hours after his team's letter flagging alleged violations surfaced, Mr Tharoor said he would like to "move on" and that it was "unfortunate that a strictly internal letter' was leaked.
Soon after counting began, Mr Tharoor's team alleged that there were "disturbing facts" in the election process in Uttar Pradesh and demanded that votes in the state be cancelled. "We did not contest this election to accept business as usual," said team Tharoor.
Salman Soz, representing Mr Tharoor's team, later said they had been "assured of a fair inquiry" had had agreed that counting should continue.
Mr Tharoor then tweeted: "It was unfortunate that a strictly internal letter to the CEA was leaked to the media. I hope this clarification by Salman Soz ends an unnecessary controversy. This election was meant to strengthen Congress, not to divide it. Let's move on."
Mr Tharoor often spoke about an "uneven playing field" while contesting against veteran leader Mallikarjun Kharge, seen to be "Gandhi-approved".
In a letter to Mr Mistry this morning, team Tharoor said: "Our campaign wants to bring to your attention extremely serious irregularities in the conduct of the election in the state of Uttar Pradesh. As you will see, the facts are damning and the election process in UP is devoid of credibility and integrity."
What happened in Uttar Pradesh "is at a completely different level", said the letter.
"We would like to underline that we have no evidence that Mallikarjun Kharge ji was aware of how his supporters were engaging in electoral malpractice in Uttar Pradesh. We are certain that if he were aware, he would never allow what happened in Uttar Pradesh. He would not allow the tainting of an election that is so important for the Indian National Congress," team Tharoor wrote.
It flagged problems like unofficial seals for ballot boxes, presence of unofficial people in polling booths and voting malpractice.
"We do not see how this election can be deemed free and fair if the tainted process of Uttar Pradesh is allowed to stand. We therefore demand that all votes from Uttar Pradesh be deemed invalid," said the letter.
By the end of the day, the Congress had its first non-Gandhi chief in 24 years. Mallikarjun Kharge won the contest, winning 84 per cent of the votes cast.
Sealed ballot boxes were brought from across the country to the Congress headquarters in Delhi.
Mallikarjun Kharge, a long-time loyalist of the Gandhi family, was seen as the front-runner in the race. This had provided ammo to critics, who alleged that the party would be remote-controlled by the Gandhis if he won.
The Congress has vehemently denied the possibility. "These (allegations) are all used by critics... Two competent individuals are competing... Every effort is being made to keep it a free, fair polls," Jairam Ramesh, the party's General Secretary-in-Charge of Communications, told NDTV.