Please see my post here:
https://www.theanswerbank.co.uk/Law/Question1639450.html
It explains (I hope) the difference between what an employer can do and what they might actually be entitled to do. (They're not the same!). It all comes down to what your employer (and, ultimately, an employment tribunal) might, or might not, regard as 'gross misconduct'.
However an employer is normally entitled to expect an employee to carry out any 'reasonable' instruction in relation to their work. Obviously an instruction to do something that's unsafe, or that's got no connection whatsoever with your actual job isn't 'reasonable' but it's likely that an employment tribunal wold regard it as perfectly reasonable for an employer to expect an employee to fill in a form relating to their work (however distasteful or pointless the employee might find that task).
So, if your employer decided to sack you on the grounds of 'gross misconduct' (for deliberately and persistently refusing to carry out a 'reasonable' instruction in relation to your work), my opinion is that you wouldn't have a leg to stand on if you took the matter before an employment tribunal.
All that is my long-winded answer. I hope that it explains the reasoning behind my far shorter one: "Yes!"