Xsara Picasso locks

[Krill]

Hi, I have a xsara picasso, no remote key but it all locks with the key in either of the front doors, the problem is if I pull the rear near side door handle all the locks undo, can anyone help please?

[wheeler]

If you mean the exterior door handle it sounds like the rear NS door is not actually locking then when you then pull the handle the door is just opening as normal. Its normal that the whole car unlocks when any of the doors are opened.
The door latch mechanisms are pretty common failures on Picassos. It would be worth checking the wiring loom where it goes from the body to the door although its not as common on rear doors if they are not used as much.