Citing letters allegedly written by Mallya to both Singh and Chidambaram, BJP spokesperson Sambit Patra demanded that Congress President Sonia Gandhi and Vice President Rahul Gandhi come clean on the issue.
Reading out the contents of the letters to the media, Patra said: "A bailout package was given to Kingfisher Airlines on Manmohan Singh's insistence."
"While an ordinary man goes through a lot of paper work and grilling to get a petty loan, Mallya procured loans worth Rs 9,000 crore without proper papers or proper accounts.
"The often-asked question was, were their certain hidden hands pulling the string from behind? Was the sinking ship (Congress) helping the sinking airlines (KFA)," Patra said.
"We now have certain emails, letters and correspondence that reveal that those hands belong to former Prime Minister Manmohan Singh and his Finance Minister Chidambaram," said Patra. The BJP leader also alleged that on "Manmohan Singh's insistence", the Income Tax Department went soft on Mallya and his accounts were also "unfrozen".
"Mallya is quite categorical in stating that certain time-critical fund releasing has to be done by the banks and the indulgence of Manmohan Singh is extremely important," Patra said reading out a letter.
"Letter after letter written to Manmohan Singh, Mallya says he needs the indulgence of the PM and certain funds are released," said Patra.
Patra also claimed that Mallya had written a letter to Chidambaram asking him to ensure that the State Bank of India grants him a no-objection certificate (NOC) allowing his company United Spirits Limited (USL) to raise over Rs 2,000 crore through issue of shares on a preferential basis.
"The SBI which did not want to indulge with a defaulter called Mallya was ready to give the NOC to the USL only because it was rebuked by Chidambaram," alleged Patra while reading out the contents of the letter by Mallya.
Patra also pointed fingers at the Congress' top leadership. "Both Sonia Gandhi and Rahul Gandhi need to come out in public and declare in whose behest the then Prime Minister and his Finance Minister sanctioned loans to Mallya. They need to come clean on this," added Patra.