Enterprise bargaining in the fast food industry has been rendered "unworkable" in the wake of a landmark decision from the industrial tribunal that saw an agreement covering Coles workers torn up for failing a key legal test, claims the Australian Industry Group.

The Fair Work Commission's application of the better off overall test following its decision in the Coles case has led to failures in enterprise agreement-making in the fast food industry.

The test requires any enterprise bargaining agreement leaves its staff better off than the basic award that covers that industry and in the Coles case the commission found that all staff had to be better off than the award.

"Such a test is unworkable for businesses that may have tens of thousands of employees who work a vast array of different shifts, often based on the personal preferences and study commitments of individual employees," AIG chief executive Innes Willox said on Tuesday night.