Apple and Google must tell users how much they are spying on them, according to US lawmakers.

The Energy and Commerce Committee has written to the heads of both companies to demand they make clear whether iPhones and Android devices are collecting information about their users, and how that data is used.

The letters suggest that devices might be tracking their users, including tracking their location and listening in to what they are doing through their microphone. It asks that both companies make clear their data policies, including whether that information is tracked and who it might be passed on to.

The letters make reference to suggestions that – despite tech companies’ claim that devices only listen if they hear their wake word – they are actually collecting more audio than that and that unknown companies might have access to recordings of people’s personal lives.

“Recent reports have also suggested that smartphone devices can, and in some instances, do, collect ‘non-triggered’ audio data from users’ conversations near a smartphone in order to hear a ‘trigger’ phrase, such as ‘okay Google’ or ‘hey Siri,'” they write in letters to the heads of both Apple and Google. “It has also been suggested that third party applications have access to and use this ‘non-triggered’ data without disclosure to users.”

A letter to Google also points to reports that Google is allowing third party companies to access information in users’ Gmail accounts.

“In June 2017, Google announced changes to Gmail that would halt scanning the contents of a user’s email to personalise advertisements to ‘keep privacy and security paramount.’ Last week, reports surfaced that in spite of this policy change, Google still permitted third parties to access the contents of users’ emails, including message text, email signatures, and receipt data, to personalize content. In the context of free services offered by third parties, these practices raise questions about how representations made by a platform are carried out in practice.”

As well as making reference to specific reports, the letters to both Apple boss Tim Cook and Alphabet CEO Larry Page including a whole range of specific questions. They delve into the technology the companies use to track users information, as well as asking general questions about the companies’ policies on how they can use the information they have collected