I've had reason to deal with Centrelink recently - Australia's equivalent of the DWP.

I've written to them twice, both times enclosing my client's written authority. They wrote to my client recently in the following terms:

"Please note that this office is unable to respond to queries about your pension from persons other than yourself unless you authorise a third party to enquire"

In addition, they ignored two phone calls and one email...

Sound familiar? Sigh...