Why are UK doctors taking legal action against their own medical board?

One of the questions bamboozling doctors in the UK is why the country’s medical board is about to start regulating unregistered practitioners pretending to be doctors.
Yes, physician associates, the new workforce who are being trained via a two-year master’s degree to work in the NHS providing services ranging from administering anaesthesia to working with GPs.
A new storm has erupted because for the first time in its 150-year history, the General Medical Council (GMC, the equivalent of the Medical Board of Australia) is about to start policing their activities on the assumption that they too are medical professionals.
The British Medical Association (BMA) is horrified and is seeking a judicial review, saying it risks a “dangerous blurring of lines”.