The EC said the defiance by a Union Minister of the Constitutional body was "unprecedented" and his "improper and unlawful action" has put a strain on the delicate balance of functions between Constitutional authorities.
The strongly-worded two-page letter was written to the President after an emergency meeting of the full Commission in the wake of Khurshid's statement earlier in the day that he would continue to pursue the line on nine percent sub-quota for minorities 'even if they hang me'.
The EC had earlier censured him for the same statement made on January 8 while campaigning in Uttar Pradesh elections, holding that it was violative of the Election Model Code of Conduct.
"The Commission is shocked that instead of being remorseful about the violation of the Model Code, that carries the consensus of all political parties and the sanction of the Supreme Court, the Minister has chosen to be defiant and aggressive. This is unprecedented," the EC letter said.