I have been falsely accused of work at something by a work colleague.?

The colleague wrote a letter to my bosses however I only found out about it third hand and not from my bosses. As there was not sufficient evidence the company did not pursue the matter however I have still not been told anything officially. My question is, do I have a legal right to be made aware of any allegations made against me and do I have the right to see the letter that was written by this work colleague so that I would then be able to raise my own grievance against them?