Rescue party: The wags are out in force at the Dogs Trust's Oscars

Leggy blondes with Mustique tans and Mayfair highlights chat to clean-cut chaps in good suits as waiters weave between them bearing canapés and flutes of champagne. So far, so west London cocktail reception, until a small commotion breaks out as one particularly exuberant guest knocks a picture from the wall and another is politely restrained from urinating in the corner. Not entirely outside the natural order of things – but it is barely 8pm.

Any bad behaviour on the part of tonight's VIPs is instantly excused, however, since the guests of honour at this esoteric little bash are of the four-legged, man's best friend variety. Now in their third year, the Dogs Trust Honours recognise the achievements of dogs that the charity has re-homed; and this cocktail party is their charming, if slightly bonkers, culmination; bringing together the owners and their rather bemused-looking canines with the Trust's benefactors and a smattering of dog-loving celebrities. '

Crufts it ain't. Most of these mutts would have more luck getting into the Groucho than the Kennel Club proper and – barring the "Star in the Making" category – there are no prizes for fancy footwork or prettiest face. Instead, the awards highlight those aspects of human-dog relations that produce such a peculiarly strong bond between the species, from obedience and sheer utility in the case of dogs working with the emergency services, to examples of simple companionship that have had a profound effect on their owners' quality of life.

Much of it is unashamedly sentimental; think Pride of Britain for pooches. You'd have to have tear ducts of steel not to mist over a little listening to how Treacle, winner of the Dogged Devotion prize, curls up next to her five-year-old owner while she undergoes 12 hours of dialysis each night.

And I more or less lose it completely upon hearing that Tim, winner of the Golden Oldie award for his work in nursing homes for dementia and Alzheimer's sufferers (apparently he answered to any name), would not be collecting his award as he died the week before – without ever knowing he'd won. Frankly, it's enough to make you question the existence of a benevolent god.

Of course, pulling on our heart-strings is a pretty good way to give our purse-strings a corresponding tug – vital for a charity that cares for 16,000 dogs a year at its re-homing centres and whose policy is never to put a healthy dog down.

Perhaps even more engaging than the stories, though, is the series of portraits that photographer Dan Burn-Forti has produced to celebrate the event, a selection of which are showcased here, capturing the prize winners, the nominees and an assortment of doggy faces from the Trust's 16 re-homing centres. It is hard to say whether the individual characters which seem to leap from the simple set-ups are the work of our own human imaginations, but there is nonetheless something wonderfully, guilelessly expressive about all the dogs photographed.

Burn-Forti, who is usually to be found snapping pop stars and actors for glossy magazines, agrees that part of what makes dogs good subjects is their natural physical openness: "Unlike humans, they haven't learnt to hide what they are feeling, so you can tell very clearly in the photos if they are happy or scared and you know that it's genuine. There's no façade, they just give you their 'inner dog'."

Burn-Forti has photographed an assortment of animals over the years, from ferrets to lizards, but admits to a soft spot for canines: "I really got into dogs when I got my own dog about five years ago. I find other animals interesting, but I actually like dogs and I think you can tell from my pictures; what I try to capture in dogs might be intelligence or loyalty.

"When I did a series of cats a while ago, I kept looking at the shots and saying, 'Yes that's it, he looks really evil.' I was always trying to capture their inner baddie."

What most distinguishes Burn-Forti's pictures for the Dogs Trust, though, is that despite an undeniable "Aaw" factor, they never descend into saccharine Hallmark territory. "I try to light them in a way that isn't too fluffy," he explains. "There is more of a sense of gravitas if you have a light and dark, chiaroscuro thing going on. And I try to shoot it either from their eye level or below, because as soon as you start looking down at them, that's when they ' start looking like a cutesy pet. There is a bit of cheating involved – you are trying to find a picture that says something authentic about the dog's character, but it's often a matter of grabbing a moment between two random actions. The dog will be gnawing his bottom and then he'll just lift his head and you'll get a great shot. You somehow end up with something that I think is truthful."

He concedes that there is some truth in the "children and animals" adage: "Photographing dogs and kids is quite similar – they get bored very quickly so you have five or 10 minutes to get their attention and then they have had enough."

Not surprisingly, however, it's the pushy parents who often pose the main challenge. "The police and rescue dogs are incredible and will respond to the slightest command," says Burn-Forti, "but the ordinary dogs obviously are a little less disciplined. I suspect [it's down to] lots of doting owners who let them sleep on the bed at night.

"Everybody always thinks their dog is failing in front of the camera, so I'll be trying to get the dog's attention and everybody will start trying to encourage them, too, which just results in masses of confusion. Some of them came with whole entourages – it was like photographing 50 Cent."

For more information: dogstrust.org.uk