In what's considered a New Zealand first, Christchurch businessman Mike Pero has successfully argued a conflict of interest case against his own law firm.

The entrepreneur had taken Wellington lawyers Buddle Findlay to the High Court after learning they were acting against him in a dispute with a business partner, despite being his own lawyers for many years.

In a decision released last night, the judge acknowledges there was a conflict of interest and has found in favour of Pero.

Mike Pero believes the judgement confirms Buddle Findlay was acting unethically, and unprofessionally, as no business should attack a client who is still paying for their services.