It's a complex situation with regards to animal welfare. A dog barking is not considered a cruelty issue, and doesn't directly indicate a dog is simply distressed. RSPCA will not get involved due to barking, and as long as the dogs have water, shelter and are not in danger, the best they will do is leave a card.

I have 2 dogs who are left for various periods of time a day, there have been some very long periods in the past due to extreme reasons, but in general I keep it to a minimum.

You would be surprised how few dog owners know anything of their dogs behaviour when they are gone. Most assume if all is well when they leave the house, that's how it remains. How wrong some can be.

Even as a dog lover I find dogs barking constantly an irritation, so can empathise with the OP about this totally.

Hope you find a solution to it, but don't rest too much hope on legislation or rules, it's just not there.