Customers should be kept informed about any plans from broadband providers to monitor online activity, one research organisation has said.
The World Privacy Forum has suggested that ISPs offer customers the option to opt-in or out of systems such as Phorm.
BT held a secret trial of the behavioural online marketing program last year, which attracted criticism from users and commentators.
As a result the European Commission is now investigating the incident and the way EU laws regarding online privacy are upheld in the UK.
A spokesperson for the World Privacy Forum said it is imperative that broadband providers seek out permission before running such a program.
"Internet providers should offer their customers a choice regarding Phorm, and make it clear and upfront," the representative said. "I think most internet users would decline to participate in Phorm if given the choice, which ought to be the case."
Online retailer Amazon announced this week that it is to block Phorm from scanning its web pages to monitor user activity.