Sale Sharks: Players reported over 'team leaks' before Bristol match
Sale have complained that one of their players passed team information to Bristol before their Premiership match on 1 January.
The Sharks have lodged a protest with the Rugby Football Union, claiming the player - understood to be former Bristol wing Tom Arscott - released confidential details.
They have also made a complaint against the Bristol player involved.
Bristol won 24-23 at the AJ Bell Stadium after trailing 15-0.
The Sharks have lost their past 10 games in all competitions.
A statement from Bristol said they had been "made aware of a complaint from Sale Sharks, which is now being investigated by the RFU".
It added: "The club are absolutely confident of no wrongdoing in this matter and will fully co-operate with the investigation."