Employers and legal experts questioned this week whether the mediating body that will resolve union recognition disputes can do its job properly.
The claims came after it emerged that firms fighting recognition rights with unions will be told by members of the Central Arbitration Committee not to tell them everything, as it may have to use that information against them later.
The revelation questions the ability of the CAC to play any meaningful role in helping employers and unions reach an amicable agreement on recognition - one of its main duties.
The problem is caused by the CAC's conflicting role as both mediator and judge. Its first duty is to act as go-between, listening to each side's position and trying to broker an agreement.
It will consider which employees should make up the bargaining unit and how the process should work when a union makes a claim for recognition.
But if an agreement cannot be reached it will act as judge and impose a decision. Anything it has learnt in the mediation process will influence its decision.
Raymond Jeffers, head of employment law at Linklaters said the CAC's role as mediator will be compromised as employers will not be able to speak freely.
Sir Michael Burton, chairman of the CAC admitted that it will have to advise employers not to tell it certain things. "We will have to say there are certain facts that we won't be able to put out of our minds," he told Personnel Today. "We may say to someone 'don't tell us that, keep it for Acas or for yourselves'."
Michael Gooddie, HR director at GNER and an expert in industrial relations, said the success of mediation depends on honesty and openness.
"Everything has to be brought out into the open. What is not brought out will potentially wreck the process downstream," he said.