Mr Kejriwal alleged that 300 machines were sent for the Madhya Pradesh by-polls from Govindnagar constituency in Kanpur in Uttar Pradesh, the state where elections were held recently.

"Technically, EVMs can't be used or shifted 45 days from poll results. So what was the Election Commission's compulsion to shift the machines from UP to Madhya Pradesh?" Mr Kejriwal questioned, insisting that EVMs shouldn't have been shifted from UP before April 26 - 45 days from the March 11 verdict.

AAP alleges that tampering on a "massive scale" was exposed in Madhya Pradesh's Bhind. The Election Commission has ordered an investigation and transferred two top officers and three policemen after an EVM from Kanpur reeled out BJP voter slips during a demo for journalists in Bhind on Friday.

"We challenge the Election Commission to make the EVM available to us for 72 hours. We will read the code and rewrite it too," said Mr Kejriwal.

The Election Commission has rubbished the allegations, saying the faulty VVPAT machine was one of the many on reserve for the UP polls. No EVM was sent from Uttar Pradesh for use in the Madhya Pradesh by-elections, it said.

According to media reports, BJP slips came out on pressing different buttons on the Voter-verifiable Paper Audit Trail or VVPAT machine during the demo.

The VVPAT machine pushes out slips with the party symbol that a voter chooses by pressing a button. The slip drops into a box and cannot be taken by the voter. If the slips don't reflect the voters' choice, they can file a complaint with the Election Commission, which has to immediately stop voting if the claim is correct.

Opposition parties allege that the Bhind incident proves that tampered voting machines had a role in the BJP's giant victory in Uttar Pradesh. They also allege that Election officer Saleena Singh threatened journalists with detention if the news was reported.

On Sunday, the Election Commission hit back at AAP and said in a strongly-worded letter that the party should "introspect" why it didn't perform well in the state polls instead of blaming EVMs.