Criticised for giving a wrong report in the Bhushan CD case, the CFSL Delhi today hit back saying the CD containing alleged voice of Shanti Bhushan was subjected to "detailed and extensive examination" and its report can only be "challenged" in the court of law.

Sources in the central forensic science laboratory, Delhi said the alleged CD was examined at CFSL, which is the premier forensic laboratory of the country by four Forensic voice identification and authentication experts, who have, after detailed and extensive examination, submitted their report to the Delhi police.

"The matter is still under probe by the Delhi Police and the report of the forensic experts can only be challenged in the court of law," said a CFSL official.

The case relates to a CD which had circulated ahead of the first meeting of the joint drafting committee on Lokpal Bill which had purported conversations between Bhushan and political leaders Mulayam Singh Yadav and Amar Singh over fixing a judge for Rs four crore.

Bhushan had claimed that the CD was fabricated and got it examined by a private laboratory, which said the CD was fabricated. A copy of the disc was sent by the Police to CFSL, Delhi which reportedly said the CD was genuine.

The Police sent it for a second opinion to CFSL, Chandigarh which reportedly said it was a cut and paste job.

Earlier, Shanti Bhushan in a letter today to Prime Minister Manmohan Singh demanded that the report of CFSL Chandigarh be made public and action be taken against four experts who had signed the Delhi CFSL report.

"You are requested to get a prompt enquiry done and get the four experts who have signed the report, declaring the obviously fabricated CD as authentic, removed from their posts to salvage the reputation of the Delhi CFSL," Bhushan said in his letter.