E-mails between the ministry and Phorm show the department asking if the firm would be "comforted" by its position.
Home Office e-mail to Phorm:
"If we agree this, and this becomes our position do you think your clients and their prospective partners will be comforted"
The messages show Phorm making changes to the guidance sought by the ministry.
In an e-mail dated August 2007, an unnamed Home Office official wrote to Phorm's legal representative and said: "My personal view accords with yours, that even if it is "interception", which I am doubtful of, it is lawfully authorised under section 3 by virtue of the user's consent obtained in signing up to the ISPs terms and conditions."
In an e-mail dated 22 January 2008, a Home Office official wrote again to Phorm and said: "I should be grateful if you would review the attached document, and let me know what you think."
Lib Dem Home Affairs spokeswoman Baroness Sue Miller, who has questioned the Home Office about Phorm, said the e-mails were "jaw dropping".