"Don't use EVMs in Gujarat and other polls that are slated to be held. EVMs are under suspicion," Mr Azad said in parliament, adding, "If they would have rigged in all five states, they would have gotten caught, so they rigged EVMs only in the largest state UP."

"They have lost their mental balance," retorted union Minister Mukhtar Abbas Naqvi. "The same EVMs were there in 2009 and earlier. The opposition is questioning the credibility of the Election Commission," he said.

The minister also said, amid uproar in the government benches, that BSP chief Mayawati had "insulted democracy and the people," by calling the BJP "beiman (cheats)."

It was Mayawati who first made allegations of rigged EVMs soon after the UP election results were announced. The BJP has won 325 of UP's 403 seats along with allies, leaving very little to be shared among the rest. Ms Mayawati had to settle for 19 seats.

The Congress' Digvijaya Singh brought up the issue in the Rajya Sabha today when he talked about reports that an EVM tested for a by-election in Madhya Pardesh's Bhind recently only issued slips with the BJP symbol. The EVM was shipped from Kanpur in UP, where it was a reserve machine for the assembly elections.

Digvijaya Singh demanded that only ballot paper be used for the by-elections in several states this month and in elections hereafter.

Union Minister Prakash Javedkar said the Election Commission has made it clear that there can be no manipulation of EVMs and that the opposition should raise its concerns with the poll panel and "not waste parliament's time."

Earlier this week, Delhi Chief Minister Arvind Kejriwal alleged that the Bhind test proves that EVMs were tampered for the UP elections. He offered to demonstrate how the machines can be rigged and demanded that only ballot paper be used for civic elections in Delhi later this month.

Mr Kejriwal has earlier also said he suspected that EVM tampering may have led to his Aam Aadmi Party's poor performance in the Punjab assembly elections.