The Congress on Tuesday demanded that at least half of all voter-verifiable paper audit trail slips, or VVPAT slips, in every parliamentary constituency be randomly counted to verify votes. At present, 10% of VVPAT slips are randomly selected for the purpose.

Voters be “fully assured that the process has some sanctity and the credibility” only when this is done, party spokesperson Anand Sharma said at a press conference in New Delhi. “It is important that the elections are not only free and fair but the voters must also believe that it is free and fair,” he added.

Opposition parties have raised doubt about the credibility of electronic voting machines a number of times in the last two years. However, the Election Commission has repeatedly denied that the machines can be tampered with.

The controversy surrounding the machines blew up on Monday, when Syed Shuja – a self-proclaimed cyber expert – claimed in London that he could demonstrate that the machines could be hacked. He even claimed that the Lok Sabha elections in 2014, which the Bharatiya Janata Party won with a simple majority, were rigged.

The doubts that Opposition parties have must be addressed, Sharma said. “No country in the world except for four now, has machine voting,” he added. “Even the big European countries have gone back to the paper balloting. There is some merit in this demand but in the interim until this issue is finally addressed which one day it has to be, at least 50% of the VVPAT slips must be randomly counted in every parliamentary constituency, not 10%.”

Earlier in the day, Union minister Ravi Shankar Prasad had dismissed Shuja’s claims and accused the Congress of organising the event in London. Prasad also questioned Congress leader Kapil Sibal’s presence at Shuja’s press conference.

Sibal address the media a few hours later and said the claims against him had compelled him to do so. The Congress leader read out excerpts of claims from Shuja’s statement and described it as a “science fiction story” that can be verified. He said he attended the event because he was in the city for another event and had an invitation from one of the organisers.

“Indian Journalists Association London President Ashish Ray told me he has sent invitations to all political parties including BJP and the Election Commission,” ANI quoted Sibal as saying. “I told him [Ray] that I will be in London for some personal work and he insisted that I should come as they are going to make an important revelation. So I went.”

The Congress leader said an investigation needs to be conducted into Shuja’s claims about some murders, irregularities in the elections and the United States granting asylum to the “cyber expert”.

“The charges made are very serious. I cannot vouch for them or deny them,” Sibal said.

Meanwhile, Congress spokesperson Abhishek Singhvi said Sibal did not claim to represent the Congress at the London press conference nor did the Opposition party have any role in the organising the event.

In April 2017, 16 Opposition parties urged the Election Commission to conduct elections using the ballot system, saying allegations of electronic voting machines being tampered with had created a “deep-seated trust deficit” on their reliability.