In a statement the ICO said it wanted to find out “whether any details of individuals consulting the NHS Choices website are available to third parties”.

Blogger Mischa Tuffield, of online identity protection firm Garlik, first raised concerns about the presence of web analytics technology on the health information site and how it was used to track behaviour, while data on which web pages were accessed was being sent to Facebook as part of the ‘Like’ function.

Tuffield questioned whether it was appropriate for the NHS to be sharing such information with third parties, given that members of the public visit the site to look up medical conditions they may prefer to keep private.

The ICO noted: “There are few things more sensitive to an individual than their health information.”

A privacy statement on the NHS Choices site says that no personally identifying information is collected as part of its web analytics integration, although Facebook users who are logged in while visiting the site will have their user IDs tied to information about which pages they access on Choices whether they click the ‘Like’ button or not.

The ICO told Research it is yet to hear back from the Department of Health, though a full clarification of the situation is expected in response to an early day motion tabled in parliament on 24 November by Tom Watson MP, who had previously written to Health Minister Andrew Lansley expressing his concerns with what was outlined in Tuffield’s blog.