Kamal Nath's comment was even criticised by senior party leader Rahul Gandhi.
Former Madhya Pradesh Chief Minister Kamal Nath on Wednesday was asked by the Election Commission to explain within 48 hours his "item" remark against a woman BJP candidate.
The Congress leader had triggered a controversy earlier this week and then refused to apologise after calling the BJP's Imarti Devi an "item" even after the express disapproval of senior party leader Rahul Gandhi.
"The Commission gives you an opportunity to explain your stand in making the above said statement within 48 hours of receipt of this notice, failing which the Election Commission of India shall take a decision without further reference to you," the poll body notice said.
Earlier, Mr Nath had told reporters, "I have already clarified the context in which I made that statement... Why should I apologise when I did not intend to insult anyone? If anyone felt insulted, I have already expressed regret."
On Monday, Mr Nath had attempted to explain away the issue, saying "item" is a commonly used term everywhere, including parliament, and was not an insult of any sort.
"I just didn't remember the (person's) name... this list (in his hand) says item no.1, item no.2. Is this an insult?" Kamal Nath told reporters regarding the woman who had been a minister in his 15-month government.
"I did not say anything disrespectful. I respect women. If anyone thinks this is disrespectful, then I regret it," he added.
Imarti Devi was also among the 22 MLAs who walked out of the party with Jyotiraditya Scindia, leading to the collapse of the Congress government in March.
Mr Nath had stepped into controversy on Sunday while campaigning for party candidate Suresh Raje, who is contesting from Dabra near Gwalior against Imarti Devi.
"Why should I take the name (of the opposing candidate)? You all know that person better than me. What an item," Mr Nath had said.
While the BJP and the woman candidate have demanded Mr Nath's expulsion from the Congress, the comment has also come to the notice of the National Commission for Women, which has sought an explanation from the senior leader.
In her appeal to Congress chief Sonia Gandhi, Imarti Devi has questioned if she would have condoned the statement had it been made about her daughter.
"I want to appeal to Sonia Gandhi, who is also a mother, not to keep such people in her party. Will she tolerate it if anybody said something like this about her daughter?" she had told news agency ANI.