The UK government's response came nearly a fortnight after India made a request for the deportation of Mallya, whose Indian passport was revoked in a bid to secure his presence for investigations against him under the Prevention of Money Laundering Act 2002.
There is also a non-bailable warrant issued against Mallya.
"The UK government has informed us that under the 1971 Immigration Act, the UK does not require an individual to hold a valid passport in order to remain in the UK if they have extant leave to remain as long as their passport was valid when leave to remain or enter the UK was conferred.
The extradition can happen under the 1993 treaty or any other necessary assistance under the Mutual Legal Assistance Treaty (MLAT) signed in 1992 between India and the U.K.
However, India was hoping to get the liquor baron, who is facing arrest over allegations of defaulting bank loans of over Rs 9,400 crore, through the expeditious route of deportation and not go through the lengthy process of extradition.