NEW DELHI: Tina Ambani on Friday appeared as a prosecution witness in the 2G spectrum case and told a special court that she had "no role" in the affairs of Reliance ADAG.

A day after her husband and Reliance ADAG chairman Anil Ambani 's deposition as a CBI witness, she told the court that she has never been associated with any firm of Reliance ADAG.

"I have no role in Reliance ADAG as I am a housewife, run a hospital ... I have never been associated with any Reliance ADAG company," she told special CBI judge OP Saini.

55-year-old Tina Ambani was shown documents of various firms said to be associated with Reliance ADAG, including Zebra Consultant Pvt Ltd, Swan Consultant Pvt Ltd.

She, however, said she does not have "any knowledge" about these firms.

During her examination-in-chief by CBI prosecutor KK Goel, she was shown various documents related to the case and she identified her signatures on them.

When she was asked to identify the signatures of Anil Ambani on some of the documents, defence counsel objected to it saying when the Reliance ADAG chairman had already identified his signatures then why was she being asked to identify them.

Senior advocate Harish Salve said that it seems that CBI is "doubting" Anil Ambani's signatures.

"They bring a witness and do not trust his/her memory. What is this?," Salve said, adding, "If he has appeared and has identified his signature then why are they showing her (Tina) his signatures. Are they doubting his (Anil Ambani's) signature?."

To this, the judge told Salve, "I agree with you." On Thursday, Anil Ambani had deposed as a CBI witness in the case during which he resiled from a statement made during the probe and "did not support" CBI's case.

In his four-hour long deposition, he had denied that Swan Telecom was a front company of his group RADAG for securing the precious radiowaves.

Since Anil Ambani had not supported CBI's case, the agency decided not to drop Tina Ambani as prosecution witness saying he "has not supported the prosecution case" requiring her to stand in the witness box.