Don Foster, the Liberal Democrat shadow secretary of state for culture, media and sport, has written to the chairman of BT asking him to explain his firm's secret trial of Phorm's advertising technology last summer.
Meanwhile William Hague, the Conservative's shadow foreign secretary, has written to the Department for Business, Employment and Regulatory Reform, voicing constituents' opposition to the deals signed by BT, Virgin Media and Carphone Warehouse to spy on the web browsing of millions.
Foster said today: "It is essential BT are open and honest about their activities last summer. The relationship between Internet Service Providers and their customers is based on trust.
"A secret test would seriously threaten that relationship and undermine BT’s integrity."
BT has admitted it misled customers and the media over the secret trials. A BT Business subscriber in Weston-super-Mare got in touch with The Register last July after spotting suspicious redirects to a domain owned by Phorm. At the time BT denied any relationship with the ad-targeting company.
Foster called on BT's Sir Michael Rake to ensure that when the nationwide Phorm system goes live it is on an opt-in only basis, as demanded by Sir Tim Berners-Lee, the inventor of the web. He has also written to Virgin Media and Carphone Warehouse with similar appeals.
Two parliamentary questions to the secretary of state at BERR, John Hutton, have also been tabled.
The constituents who raised the Phorm issue with William Hague have written about it here. We've reproduced Don Foster's letter to Sir Michael Rake here. An early day motion on Phorm he will propose MPs sign is here, and you can contact your own MP using this website. ®