"Look at Congress' compulsion, they have to get people out of jail to fight election... this is the situation of their allies," Modi said addressing a 3D rally.
"In Bihar, their whole campaign is depending on people taken out of jails," he said.
"These are the worst days for Congress. They thought Manmohan Singh government was being tainted and they would escape... But they are paying for their sins," Modi said.
The Bharatiya Janata Party slammed the Congress for targeting him, and questioned if they have no issues left.
"Is insulting Modi an election issue? Would you seek votes on the basis of what Modi is saying, or what Modi is doing? Political criticism has always been there but never before have votes been sought by insulting one person. This shows the bankruptcy of Congress," he claimed.
The BJP leader also said that the voters in the last phase of election on May 12 were the most crucial, as they would make the final decision.
Varanasi, which is Modi's second Lok Sabha seat, votes May 12, on the last day of Lok Sabha poll.