[pthr]

You don't have an HR department you can discuss with? Just be fully transparent and present your own perspective, all of it. If your HR is professional, they will help getting to the bottom if this. Their job ultimately is to optimize the workforce's output. If your manager is jeopardizing your own contribution to the company, he is not doing a good job and HR should make him see that. One ideal outcome would be an open talk with HR, manager, the trash talker and yourself, in which you all clearly define your personal objectives (what do you want to realize / where in the company do you want to be); could even turn out that these can perfectly co-exist.

[toomuchtodo]

HR exists to protect the business. Do not do this. Odds are very high you will get blown on the door asap after this conversation. OP should be looking for their next job immediately while establishing a robust paper trail in the event they can demonstrate a hostile work environment or illegality at their current employer.

They've got no leverage. They need to protect themselves and derisk.

[bityard]

I hope this doesn't come off as overly cynical, but this is a wildly popular misconception about what HR is for and does. Google "HR is not your friend."

Some companies might have a mediation program to mitigate employee/manager disputes, but the vast majority do not. If OP had lost the confidence of their manager and doesn't see any options to regain it, then there is nothing left but to move on.

[pthr]

If that's so I should never leave my company. My own situation wasn't directly comparable but I was stuck in a role I ended up in; HR helped me out big time. There core focus was: how do we make everyone excel in what they do, accepting naturally that every individual has its own weaknesses.

[bityard]

That's an excellent philosophy and I wish more managers/business had it.