Congress on Tuesday demanded that BJP leader Subramanian Swamy be questioned in the wake of fleeing of Vijay Mallya from the country as the controversial businessman was "national working President" of his now defunct Janata Party between 2003 and 2010.

"Mallya and Swamy have deep-rooted relations wherein Mallya was the national working president of Swamy's Janata Party during 2003-2010," party spokesman Pramod Tewari told reporters.

He said Congress has been raising serious but yet-to-be- answered questions about the "complicity" of the government in letting "Mallya escape from the bounds of Indian law and law enforcement agencies".

"We would like to further ask if the Prime Minister's favourite rabble rouser Subramanian Swamy also played a role in letting Vijay Mallya abscond and fly off from Indian shores?" he said.

Tewari said the plot is increasingly getting "sinister" and the PM would do well to come out clean on "Mallyagate".

Swamy is the complainant in the National Herald case in which several Congress leaders, including Sonia Gandhi and Rahul Gandhi, have been made accused.