The recording, first reported by the Daily Mail, shows Mr Blackford and other MPs declaring their support for Patrick Grady, who was found to have breached Parliament’s sexual misconduct policy for making an “unwanted sexual advance” to a teenage staff member.
In the tape, which emerged from the SNP party’s group meeting, Mr Blackford reportedly says he "would encourage" his fellow MPs to give "as much support as possible" to Mr Grady.
Now chief whip Owen Thompson has reportedly sent an email to all SNP MPs claiming whoever made the audio relating to Mr Grady has legal questions to answer.
The email from Mr Thompson there were “serious questions to be answered on the legality of sharing a recording without consent under terms of the Regulation”, The Times has reported.
The correspondence is alleged to have been sent at 11:34pm on Friday, with the leak of the recording first reported on Saturday.
All SNP MPs who attended the group meeting have been asked to speak with Mr Thompson either on Tuesday or Wednesday.
Mr Grady, 42, was found by an independent panel to have touched and stroked the neck, hair and back of a colleague 17 years his junior at a social event.
The man targeted by Mr Grady, who was 19 at the time of the incident, has said he is “bitterly disappointed” at the “lenient” sanction.