I think you should phone the RSPCA, however, i would not be entirely surprised if there is very little they can or will do. This is mostly because very often, unless there are visible signs of severe abuse or neglect, their hands are tied. I could be wrong.
Has the OP seen these dogs like this on more than one occasion? If she has then yes, phone them. If not, maybe go back and "keep an eye".
We don't know anything about the owner of these dogs. I am a bit surprised there is wee and poo tbh - i used to have a rottie and, rightly or wrongly, used to leave him indoors all day on occasion - he always managed to wait til we got home. Most days someone took him out for a walk at mid day. There could be lots of reasons why these dogs are being left in the porch though.
Is there absolutely no access to outside? or even inside?
I would be inclined to intervene - it might be that the owner of the dogs is actually no longer able to take care of them due to illness? Unsure what to do for the best? In those circs, they might actually APPRECIATE a visit from the RSPCA and something can be done. If they are just shit dog owners, unless the dogs are showing physical signs of neglect there will be very little that can be done sadly.