Campaigners say ticket resale company Viagogo is not fully complying with a court order to reform its practices.
In November, the firm was required to improve the information it gives to consumers, including details of the seller and seat numbers.
The company now insists it is compliant with the legal requirements.
But ticketing expert Reg Walker said Viagogo had not fulfilled its obligations and "seems determined to sit outside the law."
Last year a court ordered Viagogo to "overhaul" the way it does business following legal action by the Competition and Markets Authority (CMA).
Under the court order Viagogo was obliged to:
- Tell ticket buyers if there is a risk they will be turned away at the door
- Inform customers which seat they will get
- Inform buyers who is selling the ticket
- Make it easy for people to get their money back when things go wrong
- Prevent the sale of tickets a seller does not own and may not be able to supply
- Not give misleading information about the availability and popularity of tickets
The deadline for Viagogo to comply with the order was mid-January - the same date by which other resale sites had agreed to change their practices.
On 17 January Viagogo announced that it had met the deadline and was now compliant.
"All tickets on Viagogo are valid and it is perfectly legal to resell a ticket or give it to someone else if you want to," the company said.
Why is Viagogo being criticised?
Some ticketing experts and consumers say Viagogo is failing to fulfil its obligations as set out by the CMA.
Adam Webb from the FanFair Alliance accused the company of "minor tinkering" rather than the "complete overhaul" expected.
He said they have failed to make information transparent and to provide all details required - like seat numbers, trader contact details or provisions of resale restrictions.
Fans might be able to discover who was selling the tickets - but only after they had started the buying process, he said.
"They [Viagogo] should show you who the trader is from the get-go,
"Trader contact details are not supplied. Viagogo only give you a name, or an initial. This is in breach of the 2002 eCommerce Directive."
Mr Webb suggested Viagogo was making misleading marketing messages about the demand level for certain events.
Ticketing expert Reg Walker, from the consultancy Iridium, described as "nonsense" Viagogo's assertion that they are compliant with the court order.
"When you look at the relevant legislation in the Consumer Rights Act - which I helped draft - it says quite clearly that you must put your details on the website and you must have the seat, block and row," he said.
"It means every single listing on that website that does not contain these details is an offence. Viagogo seems determined to sit outside the law."
What happens next?
According to the CMA, if Viagogo fail to comply with the court order the company could face a fine.
If particular, if serious breaches were proven then the court has the power to send certain individuals to prison.
CMA chief executive Andrea Coscelli has said the watchdog would "not hesitate" to take action against companies that failed to meet their obligations.
Campaigner Claire Turnham was awarded an MBE after obtaining close to £1 million of refunds from the site through her Victim of Viagogo group.
She said she expected the CMA to act "swiftly and strictly" if Viagogo were found not to be compliant.
"As consumers, we are desperate to know ticket buyers will be able to buy tickets more safely and have certainty that they will be protected by the law," she said.