Financial services, broking and wealth management software company GBST has taken the unusual step of asking potential suitors to propose an "exclusivity deposit fee" in order to gain access to due diligence.

The odd request from the company was made after rival Bravura, which increased its non-binding conditional indicative proposal to $3 on Thursday, put a 30-hour timeline on the company to grant it exclusive due diligence, or it will withdraw its proposal.