The Congress on Saturday urged Election Commission to book Prime Minister Narendra Modi for allegedly violating the model code.
The party alleged that the Modi held a road show in Varanasi without prior permission.
The EC, on its part, has sought a detailed report on the issue from state poll authorities.
In a complaint to the EC, the Congress alleged that Modi took out the road show in Varanasi from BHU (Banaras Hindu University) "without the necessary permission from the competent authority".
"It is requested that action may be taken and FIR registered against all BJP leaders including Narendra Modi who were part of the road show," said K C Mittal, AICC secretary incharge of legal and human rights cell.
The Election Commission said it is ascertaining the facts and will act further on the basis of the report.
"We are ascertaining the facts. We have asked the state poll authorities to send a detailed report on the issue," Deputy Election Commissioner Vijay Dev told PTI.
The opposition party said the entire video recording of the road show has been shown by various channels and election authorities must also have recorded the same.
Mittal said the road show covers three assembly seats of Varanasi South, Varanasi Cantt and Varanasi North and Modi also visited the Kashi Vishwanath Temple and Kaal Bhairo Temple during the event.
"All this was done without any requisite permission for conducting the road show from the competent authority of the Election Commission," Mittal told PTI.
On a whirlwind day in his Lok Sabha constituency to rally voters around the BJP in eastern Uttar Pradesh, Modi took out a road show, offered prayers at the two historic temples and paid tributes to Hindutva ideologue Madan Mohan Malviya today.
His road show was held on a day when 49 constituencies went to polls in the sixth phase of UP Assembly elections and people in large numbers turned out as Modi's cavalcade moved at a snail's pace.
BJP leaders believe the event, broadcast live on most regional TV news channels, will help their cause when the 40 remaining seats go to polls in the final phase on March 8.
The seven-phase assembly polls in UP end on March 8 and results will be out on March 11
(With inputs from PTI)