The Central Bureau of Investigation on Saturday interrogated BJP leader Mukul Roy in connection with the Narada tapes scandal, agency sources said.

Roy was questioned for nearly three hours at CBI's Nizam Palace office in Kolkata, they said.

'As a law-abiding citizen, it is my duty to cooperate with the investigative agency. I will come whenever called again,' he told reporters, while leaving the CBI office.

Roy, a founder member of the ruling Trinamul Congress in West Bengal, had joined the Bharatiya Janata Party (BJP) in November last year.

The former railway minister said he was not involved in the 'conspiracy hatched by Trinamul Congress supremo Mamata Banerjee... I have not taken any money.'

Asked whether he was interrogated together with IPS officer S. M. H. Mirza, who was arrested by the CBI on Thursday in connection with the same scandal, Roy said, 'It is an internal affair of the agency. It is not proper for me to comment on this.'

In the Narada videos, released ahead of the 2016 West Bengal assembly polls, persons resembling senior Trinamul Congress leaders and Mirza are seen accepting money from the representatives of a fictitious company in return for favours.

Roy alleged that Banerjee, who is also the chief minister, had been instituting 'false' cases against him, which hold no ground in the courts of law.

Mirza was the superintendent of police of Burdwan district when the sting operation was conducted by Mathew Samuels of the Narada News portal.