If the eschution doesn't fit tight up to the tiled wall, then the plumber didn't install it in the right location.
If the tub isn't installed level, water can run along the tiling flange and leak out.
I'm assuming this is a tub/shower. When it was tiled, what is on the walls, and how was it installed?
If the plumber did the entire install, he is responsible to fix it.
can you post a picture or describe where you think it is leaking?
Could it be as simple as not having the shower curtain pulled all the way across? or are there glass doors?
Take a level and measure the tub from L-R and inside to outside from the top rim...it must be level.