In a memorandum, it alleged that the National Investigation Agency (NIA), which is probing the case, has completely ignored the alternative theories and has ruled out the possibility of any political conspiracy.
Heavily-armed maoists had attacked a convoy of Congress party leaders on May 25, 2013 at the Jagdalpur-Sukma highway in Chhattisgarh when they were on a 'Parivartan Yatra'.
"The NIA has even not compared and investigated the security arrangement on previous days i.E. May 23 and 24, 2013 in Bastar region where the Parivartan Yatra was provided with better security," the memorandum said.
It is necessary that CBI is asked to investigate any conspiracy angle or other security lapses that happened in the incident, the memorandum said.
The delegation was led by party's Treasurer and senior leader Motilal Vora and comprised Rajya Sabha MP from the state Mohsina Kidwai, Chhattisgarh Congress chief Bhupesh Baghel and Leader of Opposition in the state Assembly T S Singhdeo among others.
