How to blur everything but not the object?

How could I blur everything in the scene but not the specific object?

I know you can have selective effects like here the bloom effect: three.js webgl - postprocessing - unreal bloom selective
how to create this for blur (everything and background but not the one object).

Three.js or Fiber, doesn’t matter, I need to understand the concept.

One of the option is to place a big plane geometry behind the object and make it semi transparent.
If planning lot of camera movement or if you are going to use orbit controls then attach this plane to camera.
Eg: with plane/ with blur

Eg: without plane/ without blur

Thx Vasanth, this is a nice hack, but it does not work when you have left and right other objects… or when you have orbit controls (ok you could add the plane to the camera as a child).

Any other solutions? I think it must be done with post processing and masking.