My current employer is threatening to sue me because I have raised a grievence about his behaviour. I have written evidence of him abusing me and he has admitted that he did abuse me on several occasions. However, when I raised a grievence about it, my managing director got involved and I have now been told not only am I going to be sacked for 'lying' but that my boss is suing me for slander/defamation. Basically my managing directors stance is that because my boss apologised to me, my grievence is not valid and I am actually vicimising my boss! Is my boss able to sue me?

Sure he can sue you but he must prove you slandered him and damaged him. That would mean he must prove any statements you made were not true. If all you say is correct you can countersue.

What is the pupose of the grievience, ( assuming you are union) but yes he can sue, but he will have to prove things you said is false, since he already admitted it, I assume you have it in writing.

But what do you want , are you asking for a change of jobs, change of bosses, shifts, asking for money ?

He can't win a suit for slander/defamation if you have proof that what you said is true.

As for being sacked, depending on where you are there are laws protecting whistleblowers. If you are fired, I suggest consulting an attorney.