Redten has been brought to book by the Advertising Standards Authority after making misleading claims of 'unlimited broadband' and 'unlimited internet downloads'.
The watchdog ruled that Redten had misled customers in advertising its packages as 'unlimited' because the ISP slowed broadband connections to dial-up speed once a 5GB or 15GB cap had been reached.
The ISP, which gives away a free PC when customers sign up for its broadband services, was also found wanting in a separate advert that offered a 'free upgrade to 24Mbps broadband'.
"Because we had not seen evidence to show that the download cap excluded only atypical users, or that customers were able to obtain an upgrade to 24Mbps free of charge, we concluded that the claims 'unlimited broadband', 'unlimited downloads' and 'free upgrade to 24Mbps broadband' were misleading," the ASA said in its ruling.
The ASA also reprimanded the ISP for its lack of response in dealing with the complaints, and an apparent "disregard for the Code".
The watchdog reminded Redten of its obligations under the Code and told it to respond promptly in future.
The ruling is the latest in a spate of problems to bedevil the ISP, including a week-long internet outage in March which left all customers without access.
Redten was recently taken over by Fatcat Communications after going into administration.
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