Amar Singh is a Rajya Sabha MP. Rajya Sabha officials, however, denied that house Chairman Hamid Ansari had given permission for Amar Singh's questioning, saying that no such request had been received.
They said that since no request had been received, there was no question of permission being granted by the chairman.
The officials also added that there may not be a need for permission for Amar Singh's questioning as the matter did not relate to his actions in the Rajya Sabha.
Amar Singh's former aide, Sanjeev Saxena, arrested by Delhi Police, alleged that the then Samajwadi Party leader had provided Rs.1 crore for getting the support of three Bharatiya Janata Party (BJP) MPs in a trust vote in 2008.
Alleged middleman Suhail Hindustani, the second accused arrested Wednesday, also levelled the same allegations against Amar Singh, saying he was the "main" man behind the scandal.
Hindustani also accused Ahmed Patel, political secretary to Congress president Sonia Gandhi, and other Congress leaders of involvement.
Bags filled with currency notes were shown in the Lok Sabha July 22, 2008, minutes before a trust vote was to take place.
Hindustani was called to a Delhi Police office for questioning and later arrested.
Saxena is understood to have told police that Amar Singh's driver Sanjay had gone along with him to deliver the money - as claimed by BJP MPs Fagan Singh Kulaste and Mahavir Bhagora.
The two were among the three MPs who had claimed they were paid to abstain from the Lok Sabha trust vote sought by the Manmohan Singh government after the Left withdrew support over the Indo-US nuclear deal.
Saxena was caught on camera paying BJP MPs Kulaste, Bhagora and Ashok Argal bribes ahead of the confidence vote.