The Gandhis, who are accused in the case along with some other Congress leaders, contended that Swamy's plea was "in the nature of a fishing and roving enquiry which is not permissible in law".
The submissions were made in the reply filed to Swamy's list of witnesses and other evidence given to Metropolitan Magistrate Lovleen in the case.
"The application preferred by the complainant (Swamy) is vague and devoid of material particulars and is in the nature of a fishing and roving enquiry which is not permissible in law.
The court, thereafter, listed the matter for further hearing on April 22 after Swamy sought time to go through the submissions made before arguments on the matter could begin.
The accused claimed, "Swamy, through this application, is seeking to summon witnesses and call for documents without divulging their necessity and desirability on the basis of the allegations made by him in the complaint.
Swamy, in his private criminal complaint, has accused the Gandhis and others of conspiring to cheat and misappropriate funds by paying just Rs 50 lakh through which Young Indian Pvt Ltd (YI) obtained the right to recover Rs 90.25 crore which Associate Journals Limited (AJL) owed to the Congress.
The Gandhis and other accused -- Motilal Vora, Oscar Fernandes, Suman Dubey and Sam Pitroda -- have denied the allegations levelled against them.
Swamy had on February 10 filed the list of witnesses
before the court which had on December 26 last year given him the last opportunity to submit the list.
The list includes the names of eleven persons including All India Congress Committee's General Secretary Janardan Dwivedi, several officials of AJL and government officials.
In a relief to Sonia and Rahul, the court had earlier rejected "as fishing enquiry" a plea of Swamy seeking a direction to theCongress party and AJL to produce certain records relating to the case.
