At an election rally in northern Uttar Pradesh state, which is in the middle of hotly contested assembly elections, Singh, seeking support for his Congress party, reportedly praised Gandhi as a new leader and said the party scion should be seen as the future of the state, the country's largest with a population of about 170 million.
The young Gandhi draws his lineage from three former Indian prime ministers. However, he is rejected by some parties as a political novice who is being thrust onto the national scene by his powerful mother, Italian-born Sonia Gandhi, who now heads the Congress party.
Responding to Singh's comments, Prakash Javadekar, a spokesman for the opposition Bharatiya Janata Party said: "What else can be expected from a man who has been reduced to the position of a regent by the dynasty, which expects him to keep the seat warm until the crown prince is ready?" the Press Trust of India reported.
"His comments are not only preposterous but the worst kind of prime ministerial sycophancy stemming from the politics of dynasty," Javadekar added.