Companies such as Amazon, Wikipedia and LiveJournal have taken the decision to block the controversial advertising technology from scanning their sites because of the privacy implications.
However, Open Rights Group executive director Jim Killock has since admitted that, even if web sites opt out of the programme, ISPs supporting Phorm will still be able to profile users visiting those sites.
"This is because Phorm can scan search requests entered in those sites, even if it cannot detect the web site pages users are viewing," Killock said.
"For example, even if Google opts out of Webwise, when a user types in a Google query and they are using BT, it will still go through Phorm before it reaches BT."
Killock added that Phorm does not gain permission from either senders or receivers of the information before it processes the data.
Phorm uses browsing information to serve accurately targeted advertisements, and is soon to be rolled out under the Webwise brand by internet service providers BT, Virgin Media and TalkTalk. However, as the time for deployment nears, the controversy surrounding the technology only seems to be increasing.
Most recently, Phorm came under attack from the European Commission (EC), which argued that UK government authorities are running foul of European Union privacy and data protection laws by not taking action against telcos that use the platform.
The EC's move initially prompted the Open Rights Group to call on large technology firms to opt out of Phorm by sending an email to Webwise.
"While we recognise that an opt-out is an entirely second-rate way of dealing with this problem, we would strongly urge you to take advantage of it in order to immediately reduce the risk of harm to your company and to your customers," said the Open Rights Group.