British Telecom has denied claims that millions of its internet customers could be at risk from hackers.
IT consultancy NCC Group had warned that software readily available on the internet could be used to crack into BT's Home Hub system, changing settings and passwords.
A hacker could use a laptop to access a private wireless network from outside the owner's house, the consultancy said.
But BT has denied there is a particular risk with their system, and says it takes security "extremely seriously".
A spokesman said: "All wi-fi networks could be vulnerable to a determined hacker who is intent on breaking the law, and of course people have to take care.
"We take security extremely seriously and give our customers advise on extra levels of security at www.bt.com/help/hub."
He branded claims that customers' bank or credit card details could be at risk as "complete nonsense".
NCC Group is a consultancy which also offers security advice to its clients.
It carries out testing of a variety of different systems using the same tricks that hackers use.