New Delhi, Feb 4 (IANS): Contending that free and fair elections have come under a "serious cloud" with EVMs a "major cause of concern", 21 opposition parties on Monday asked the Election Commission to audit at least 50 per cent of EVMs with corresponding VVPATs in all constituencies during the Lok Sabha polls.

A memorandum to the EC signed by representatives from 21 opposition parties, including the Congress, the Aam Aadmi Party, the Samajwadi Party, and the Bahujan Samaj Party, cited "suspicious activities" concerning the EVMs during the November-December Assembly polls to five states.

"Instances of EVMs and strong rooms becoming vulnerable to attacks and manipulations were widely recorded and reported.

"Added to this were incidents where there were power outages, failure of CCTV cameras at the strong rooms, detection of signals of wireless/mobile networks of a particular telecom operator in the vicinity of polling centres and strong rooms and so on and so forth," they said in the memorandum.

The parties said there are "serious doubts about the credibility of EVMs and the purity of the entire electoral process" and sought the EC to mandate physical counter check of paper trail and matching it with the electronic vote in at least 50 per cent of all EVMs, if not all.