GPs refusing to provide Medical evidence

I have an ESA Tribunal coming up for a client and wrote to his GP asking her to answer a few questions pertinent to the case. I received the following reply:

Dear Billy Durrant
RE:  XXXXXXX   dob XXXXXX
Benefits and Housing – GP letters  
The Local Medical Committee (LMC) is the body recognised by law as representative of all NHS GPs.  This letter has been produced by the LMC for use by GP Practices.
The job of GPs is to provide medical care to their patients and they are not in a position to administer nor to police the benefits system.  It is not appropriate for GPs to be asked for letters of support or letters to confirm care needs.  GPs are neither contracted nor resourced by the NHS to provide this service and do not have the capacity to do so.  Time taken up with paperwork is time taken away from direct patient care.  There are contractual and agreed methods for GPs to provide medical information to the Department for Work and Pensions, to Birmingham City Council and to other agencies.  These are sent to the GP Practice and GPs respond directly to such requests for information.  Therefore we cannot respond to your request for a letter.

Patients can have copies of their medical records but there will be a fee. You can contact the LMC if they require further clarification.

Has anyone seen this (template) letter that seems to have originated in Birmingham (I work in West Yorks) and if so how did you respond?
In this particular case, the client made a suicide attempt by driving his car into a wall when he was found not to have LCW so I think it is a bit disingenuous for them to say that it is ‘time taken away from direct patient care’ and I was thinking of replying (politely) along those lines. Any thoughts welcome.