Four senior US House Republicans have sent letters to the chief executives of Apple and Google parent firm Alphabet, asking key questions about their use of location data, mobile phone privacy practices and the handling of customer data.

Representative Greg Walden, chairman of the Energy and Commerce Committee, along with three other senior Republicans on the panel, reached out to the firms “to probe the companies representation of third-party access to consumer data, and the collection and use of audio recording data as well as location information via iPhone and Android devices.”

Alphabet has said it plans to cooperate with the committee and provide answers, saying that “protecting our users privacy and securing their information is of the utmost importance to Google,” in an emailed statement. Apple has so far declined to comment on the letter.

The letters cite reports that smartphones can, and in some cases 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.” The letters go on to say that there have been suggestions that third party applications have access to and use this non-triggered data without disclosure to users.

The letters also reference a number of recent news stories, including the fact that Google, until recently, scanned the content of emails to personalise ads, and that third parties may still have access to this data.

The letters both ask if Google Android or Apple iPhones collect audio recordings of users without their consent, and the committee has said that it “is reviewing business practices that may impact the privacy expectations of Americans.”