If you are being suspended, you have to be told why you are being suspended. If there is subsequent disciplinary action, you are usually told at your hearing what has been said about you and by whom. Only if there is a risk to the life of the person you complained about you, could an argument be made at the Employment Tribunal why that person's name was not disclosed to you.
If you then raise a grievance during the disciplinary action, you may have the right to know who has complained about you
For more advice visit www.acas.org.uk or call the Acas helpline on 08457 47 47 47