Bartercard has been operating for 23 years. So surely it would have been closed down a decade ago if their system was illegal.
You sound like a disgruntled ex-employee or ex-franchise owner.
I would want to see genuine evidence. I am sure they pay taxes etc and those using their system are multiple repeat merchants. So they are not the problem or they would not repeat their usage. Who do you claim are upset and for what reason?