A few things you need to keep in mind. 1) do you take you dog for a walk atleast 2 times a day for 30mins. This should be just walks and not to do the deeds. This will give the dog an idea that there is a specific time when he will be able to go out. This will be a good exercise for the dog too. 2) Labs are very friendly in nature. Make sure you don't keep your dog alone in the house for a long time. It is okay for a couple of hours but not something like 10 to 12 hours, this will be too much. You have not mentioned whether its a dog or bitch.
If you are already following the above steps then please let me know. I will try to help you out.