Earlier this month, Lalu Prasad had visited Patna's Indira Gandhi Institute of Medical Science.
Rashtriya Janata Dal chief Lalu Prasad's presence at a health ministry function has created a new flashpoint between the government and the opposition BJP.
On Saturday, Mr Prasad turned up at the function organised by Homeopathic Science Congress in Patna instead of his son -- Health Minister Tej Pratap Yadav, who had been invited to be the chief guest -- providing an opportunity to the opposition BJP to target the Nitish Kumar-led government.
BJP leader and former health minister Nand Kishore Yadav said this shows who was running the government and the department and "Nitish-ji should give him (Mr Prasad) the designation of 'Super Chief Minister' officially".
Mr Prasad frequent visits and "raids" at hospitals and health centres across the state is the subject of an ongoing controversy.
Earlier this month, he had visited Patna's Indira Gandhi Institute of Medical Science and verbally ordered the retrenchment of four sacked workers. He had also visited a couple of other hospitals, acting as proxy for the health minister.
The BJP has also taken a strong exception to the invitation extended to RJD President at a government function for the start of work on a bridge on river Ganga.
"What is the rationale of inviting in an official programme a person who is neither minister nor MP, MLA and who is on bail from a court in a fodder scam case?" said senior BJP leader Sushil Kumar Modi. "If Nitish Kumar is under so much of pressure from Lalu Prasad, why does not he accord status of 'Super CM' to Prasad?"
"I can't understand this opposition as it is related to the development and we invite everyone including the Union Minister Ramvilas Paswan and BJP Leaders," said Mr Kumar. "What's wrong with (inviting) Lalooji who's a former Chief Minister and leader of the Mahagathabandhan."
The RJD, which fought the assembly elections last year in coalition with Mr Kumar's Janata Dal United and the Congress, emerged as the single largest party in the state with the alliance winning an absolute majority. Mr Prasad, who cannot contest elections or hold public office because of his conviction in a corruption case, had negotiated top ministries for his sons.