However, the SP chief ruled out Amar Singh`s return to the party, from which he was expelled last year.
"It is an injustice being meted out to Amar Singh.
It is a conspiracy to trouble (SP Lok Sabha MP) Rewati Raman Singh and Amar Singh. He (Amar) helped Congress (during the 2008 trust vote) as Samajwadi Party voted in favour of the UPA. And now he is being questioned," Yadav told a press conference here.
He said Amar Singh was not involved in bribing of BJP MPs.
"We only helped by voting in their (Congress`) favour.
Did we join the government? Did Amar Singh or Rewati Singh become ministers? Had money changed hands, I would have known about it," a visibly upset Yadav said.
He said he would helpe the expelled party general secretary "in whatever way I can" to sail through the crisis.
"We helped the government, now they (Rewati and Amar) are under probe," he said.
To a question, he ruled out the return of Singh to the party. "(We are) not taking him back...he is facing injustice," Yadav said.
In reply to a poser, Yadav refused to comment on whether Ahmed Patel, political secretary to the Congress President, should also be questioned. "I don`t know," he said.
Rewati Raman Singh will be quizzed by Delhi Police in connection with the cash-for-vote scam tomorrow, while Amar Singh has already been questioned.
Alleged middlemen Suhail Hindustani, who has also been arrested in connection with the case, had reportedly approached Singh on the intervening night of July 21 and 22, 2008 for striking a deal to buy BJP MPs.