Lalu Prasad and Tejaswi Yadav released the photograph on the former's twitter account and sought to know the "truth" from BJP.
"What BJP got to say on it? Remember crores of rupees were recovered from this minister's house, whose money it was?" the RJD supremo said in his tweet.
His son and the Deputy Chief Minister also joined in the attack on Singh, Union Minister of State for MSME and MP from Nawada.
"All malpractices of dis college wre tking place probably by his encouragement. ModiJi's Minister wanted to open a Medical college with culprit," he alleged.
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Bachha Rai, Secretary-cum Principal of the controversial Vishun Roy College in Vaishali district, is said to be the main culprit in the Bihar Intermediate merit muddle which drew a lot of flak for the state across the country.
Rai was arrested last Saturday.
Controversial Arts and Science toppers Ruby Rai and Saurabh Shrestha respectively, hailed from Bachha Rai college.
(Reopens Cal 1)
Meanwhile, Giriraj Singh, as per media reports, said that he like any other politician keeps going to various places for programmes.
"The +2 exam irregularities is basically due to failure of the system under Chief Minister Nitish Kumar," he said.
Sanjay Mayukh, Bihar BJP Vice President also defended the minister.
"Government is trying a face wash by releasing photograph of Giriraj Singh with Bachha Rai which is of a social function," he said.
"Giriraj Singh is a tainted politician from whose house Rs 2 crore was recovered earlier. Bachha Rai has reportedly said he was planning to open a medical college with a central minister...Isn't it enough to show their proximity," he said while seeking a probe against the Union minister.