Arguing in the court, the lawyers said copies of Kasab's statement were "uncertified and unattested" and could not be used to frame charges against their client and six other men accused of involvement in the Mumbai attacks.
"The said documents are neither certified copies of the original nor can be used or proved under provisions of Sub-Article 5 of Article 89 of Qanoon-e-Shahdat (Pakistan's law of testimony)," said the application.
An application containing their objections was submitted on nMonday to anti-terror court Judge Malik Mohammad Akram Awan, who is conducting the trial of the seven accused in Adiala Jail in Rawalpindi.
"Kasab is not being tried jointly with the petitioner and his co-accused, thereby his statement is not admissible," it added.
During an earlier hearing, the defence lawyers also demanded that Kasab should be brought to Pakistan to face trial with the seven accused.
The court adjourned the hearing till tomorrow after hearing arguments of the defence and prosecution.
The application by defence counsel Khwaja Sultan and Sher Afgan Asadi, said the prosecution had shown "prejudice" towards the accused by using documents provided by Indian authorities for framing charges against the suspects.
"The name of Ajmal Kasab has neither been shown in the list of the accused who have been sent up for trial nor in the ones not sent up for trial or are absconding," it said.
"The prosecution has not cited any witness to prove the so-called confessional statement of Kasab, not even Mrs R V Sawanth Waguly, the lady magistrate who had recorded it, and Shree B L Waghmare, chief metropolitan magistrate, who had deputed Waguly, is not cited as prosecution witness as per requirement of the relevant law," it said.
Lakhvi's counsel further contended that the prosecution had tried to get Kasab declared a proclaimed offender in Pakistan by obtaining warrants for his arrest though it knew that he was in the judicial custody of an Indian court where charges had already been framed against him and he was "not wilfully avoiding arrest".
"The process of procuring the presence of Kasab for trial before the court is still inconclusive and the only way to procure his attendance is through the Pakistan government demanding his custody from Indian authority for the purpose of investigation and trial," the application said.
The lawyers claimed the prosecution had "deliberately" concealed Kasab's decision to retract any statement said to have been made by him.
"He (Kasab) had also not pleaded guilty to the charges framed against him and that judicial findings have yet to be given even by the Indian court," the application said.
Lakhvi is a resident of Renala Khurd in Okara district of Punjab province, while Kasab belongs to Faridkot town in the same district.
