Audiotapes that purportedly show then Manipur chief minister Biren Singh bragging about stoking the Meitei-Kuki violence had been “modified” and “tampered” with, the National Forensic Science Laboratory in Gandhinagar has told the Supreme Court.

Excerpts from the sealed-cover report were read out in open court on Monday by the bench of Justice Sanjay Kumar and Justice Alok Aradhe, which asked the public-interest petitioner to file its response to the latest findings.

The Kuki Organisation for Human Rights Trust had petitioned for a court-monitored probe into the tapes. Biren, a BJP chief minister, resigned in February.

In August, the apex court directed the tapes to be sent to the national forensic lab in Gandhinagar after noting that the Guwahati FSL had failed to say clearly whether the voice matched Biren’s.

During Monday’s hearing, Justice Kumar read out a portion of the report to tell advocate Prashant Bhushan, appearing for the petitioner, that the Gujarat lab had concluded that the clips had been altered and were therefore unfit for a voice comparison.

Bhushan said a private forensic laboratory, Truth Labs, had concluded that the 50-minute audio was unedited and that there was a 93 per cent probability that the voice was that of the “same person” (Biren).

Bhushan said the private lab’s credentials were supposed to be very good. But the bench responded that the NFSL, too, was supposed to be a premier forensic lab.

Bhushan argued that the NFSL was a government lab, under the control of theruling party.

Solicitor-general Tushar Mehta, representing the Manipur government, emphasised that the NFSL had submitted its conclusions, and said it would be unwise to “meddle” with the peaceful situation in the state.

The bench later asked the registry to provide Bhushan with a copy of the report so that the petitioner could file its response. It posted the next hearing after two weeks.

The apex court’s remit for the Gandhinagar lab was to determine whether the audio clips had been modified, edited or tampered with, and whether the voice in the disputed tapes was that of the same person featured in clips admittedly of Biren’s voice.

The Manipur government had dismissed the tapes as “doctored”, saying these were being circulated in the “likelihood of inciting hatred and mistrust amongst communities” and to “derail the peace initiatives launched by the state and centralgovernments”.

In the tapes, Biren purportedly describes how he had defied Union home minister Amit Shah’s directive against “using bombs” in the ethnic conflict and protecting those who hadlooted armouries.

Kuki-Zo organisations had protested in the community’s strongholds in Manipur and in Delhi against Biren’s “partisan complicity” in the unrest and reiterated their demand for a separateadministration.