Here's what Dogs Trust says on its site. It has a factsheet for working owners, too...
If you work full time???..is it fair to have a dog?
We are often asked if it is possible to adopt a dog from our Rehoming Centres if the prospective owners work full-time and the dog would have to be left alone all day. As a general rule, the answer is usually no. We do not recommend that a dog should be left alone for longer than four hours at a time. Even if there is a secure outdoors area where they could spend the day, they could become very bored, distressed and possibly destructive.
If you are considering taking on a puppy rather than an older dog, the potential problems can be greatly increased. If you are trying to housetrain a puppy the process becomes very complicated and drawn out (sometimes impossible) if they are not constantly supervised. Puppies particularly must have human company during the first year in order that they can be socialised and trained correctly to avoid future problems of aggression and fear. All too often these puppies grow up and then end up in our Rehoming Centres because their owners cannot cope with them any longer.
There may be some exceptions however, where we may rehome an older dog (or dogs) to a family where the owners are out all day. This may be when the owners are prepared to employ a dog walker to walk the dog and give him some company during the day, or when one of the owners is able to take him to work, so you may want to consider these options if you are desperate to have a dog.
A dog?s owner is his pack leader and without the leader many dogs become insecure and anxious. With the leader away, many dogs take on the duty of guarding the home and will bark at any noise or sight from outside all day long. Whilst this is great security, there is a good chance that it will upset your neighbours and you may end up in trouble with your local council. If you are lucky enough to find two dogs who are very? bonded? together and prefer each other?s company to that of humans, then they will be less distressed at being left alone ? however, they may not make ideal family pets. You will still have to ensure that they do not become bored and make sure that they are able to get out for ?toilet breaks?. In most cases though, it makes no difference if the dog has the company of another dog, as it is the owner that he/she misses. There are of course individuals that may not mind being left for a long period of time, but it really is impossible to predict if a puppy will end up like this.
If you are out at work all day and are planning to get a dog or puppy without making any provision for his mental and physical welfare during this time, please reconsider carefully. Perhaps it would be better for all concerned, to delay owning a dog until your circumstances have changed. If you are considering adopting a dog from Dogs Trust, please contact your nearest Rehoming Centre directly for more information and advice.