Finding fault with the Sangh's response to the Bihar Chief Minister's remarks, Singh said it places on the RSS the burden of clearly defining Hindutva to all those Hindus, who believe and practise Sanatan Dharma.
In an article on "Hindutva" mailed to the media here, Singh said the RSS has come out very strongly against Nitish Kumar.
Snubbing Kumar over his "secular face-for-PM" pitch, RSS chief Mohan Bhagwat had asked why a Hindutva face should not lead the country.
In the five questions posed to Bhagwat, Singh asked whether "destroying Babri Masjid or any other religious place is Hindutva? Is Planting bombs to kill innocent people Hindutva?
Singh also asked Bhagwat to explain the rationale behind opposing the word secularism when it is said that Hindutva is synonymous with the term.
"RSS chief must tell what was the difference between the ideals of Hindutva and the ideals of Sanatan Dharm," he said.
Singh found it "strange" that the Sangh Parivar calls him anti-Hindu although he is a practising Hindu who prays for half an-hour each day.
The Congress general secretary said there are nine temples at his ancestral house at Raghogarh in Guna district of Madhya Pradesh, where Pooja is performed each day as per the traditions of his religion.
While posing the questions, Singh also said that although he did not expect them to be answered, he would be grateful if they were replied to.