A law firm representing 100 exploited workers at 7-Eleven has warned it will take legal action unless it receives an undertaking that the confidential files of workers will not be passed on to the convenience store giant.

Maurice Blackburn wrote to forensic accountants at Deloitte who were charged with assessing the claims to seek an urgent undertaking to protect their clients from intimidation and retribution from their former bosses.

Maurice Blackburn employment principal Giri Sivaraman said he was seeking an undertaking by midday Monday May 16 not to give clients names to 7-Eleven or the firm will seek an injunction.

"It is disappointing that it had got to this point, but we don't have any confidence that 7-Eleven will do the right thing, which is why we are now seeking to take strong further action to protect these workers," Mr Sivaraman said.