BT has come under fire after it emerged that a loophole in its new Wi-Fi for business offering meant that other users could jump on and slow down connections.
The provider recently upgraded many BT Business Broadband customers' services to allow firms to offer Wi-Fi access at the office.
However, a problem has meant that some of the wireless broadband connections are free to access by any BT Openzone user, meaning that connections can be slowed down due to the added traffic.
"BT is not being very open about the way it is doing this. It is doing the upgrade and burying this news halfway down an email to customers," stormed Ken Manger, IT manager at Ulysses, one of the companies affected by the issue.
He continued: "We think they should be asking their customers to opt-in to a service like this, rather than rely on them spotting it and opting out."
According to BT, around 20,000 subscribers whose "firmware" was upgraded are potentially now at risk from the slowdown.