Sanjeev Saxena, arrested for his suspected involvement in the 2008 cash-for-vote scam and believed to be a former aide of Rajya Sabha MP Amar Singh, was on Monday remanded to police custody for three days by a Delhi court.

Special judge Sangita Dhingra Sehgal remanded Sanjeev Saxena to police custody till July 21, on the plea by Delhi police crime branch that his custodial interrogation is required to get to the bottom of the "conspiracy".

Seeking Saxena's custody, prosecution submitted that they have to question him to know the whereabouts of Sanjay, the then driver of Amar Singh with whom he had allegedly gone to the residence of a BJP MP to hand over a sum of Rs one crore.

The prosecution also submitted that they have to recover the mobile phone used during that period and to ascertain the source of money which allegedly changed hands in the scam.

Slammed by the supreme court for a shoddy probe in the cash-for-vote scam, Delhi police had made its first arrest in the case on Sunday picking up Saxena for allegedly trying to bribe BJP MPs ahead of the UPA government's trust vote in 2008.

Saxena has been booked for various offences under the Prevention of Corruption Act, police said.