We have a lovely one year old Tibetan Terrier, she is fantastic apart from the fact that we cannot get her clean at night.  Sometimes we have a couple of nights where she is clean but 9 times out of 10 when we come down in the morning there is a poo on the floor.  I have tried feeding her at different times, feeding her less in the evenings and letting her out in the night but none of this seems to work.  We go to bed at 11-12 and get up at 6am so she should be able to go 6 hours through the night.  She is clean during the day even when we go out and leave her alone.  I am very loath to put her in a crate now as I feel she will be very unsettled by this.  Any advice is greatly appreciated.  Thanks

What are you feeding her on?  This could be a factor!

Naturediet.  Dried food gave her constipation.

You say you feel she will be unsettled if crated but have you tried?  Many dogs feel it rather comforting to be in a secure enclosed space.

Do you have a command for her pooing? I would try asking her to go during her last toilet break if she hasn't yet in the evening. Sometimes my dog sort of forgets to completely eliminate his unused dinner in the evening so I remind him to do so before bed. Much better than being woken up at 2 am by a dog needing to go out. If that doesn't work then I would go back to treating her like a puppy who can't hold it and get up early enough for her to be clean. Take her out, give the command and reward her.

she sometimes does poo just before she goes to bed but still manages to poo in the night as well!

Hi Caroline, my bitch had the same problem until I put her in a crate at night.  Dogs do not generally mess in their beds and so they wait until let out.  If you try this, when you let her out in the morning say a specific word, my word funnily enough is 'quickly' because standing at the door late on a winters night, it would be the word I would say and she would eliminate.  Now I only have to say the word 'quickly' and she performs...
It's worth a try.
Good luck

I agree, its worth trying a crate. The poo could also be anxiety for being left alone at night. A crate can be comforting if introduced properly, and as is said before, they wont want to mess a small area. Perhaps your dog doesnt realise that it shouldnt poo at night in the house.