Noting that Yadav's "antecedents and credentials at the time of his appointment in 2011, and now stands substantially altered", the ministry in its notice yesterday asked him to provide an explanation within seven days before initiating further action.
The notice said Yadav has not only "joined a registered political party as an office bearer but has also participated in political forums organised by the aforesaid party".
He said he would respond to the show cause notice served by the Ministry "but would certainly not step down from his post".
Yadav said he had informed the then HRD Minister Kapil Sibal and other officials about his intention of joining the party. Sibal made way for M M Pallam Raju who took charge of the Ministry last October.
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Sources in the Ministry said they were unaware of his political attachment till they were informed by a senior Congress leader through a letter in May.
He has been vocal about several policies the ministry has initiated.
"I had opposed coming up of an inter-university centre on teacher training institution in Kakinada which is the constituency of the HRD Minister," he said.
Slamming the ministry and the UGC, he said their policies go against the spirit of higher education be it in the matter of entry of foreign institutions from the back door or imposition of academic performance index scores in universities in a non-autonomous.