I'll caveat this by saying that I'm a regular volunteer at two local soup kitchens, as well as making up kit bags for the homeless on my travels. I've been working in one of those kitchens now for around 15 years and in that time I can tell you that there are the perpetual homeless. For a variety of reasons they will always end up back on the streets. Each case is unique and also quite sad. It isn't usually down to any one thing but a combination whereby they simply can't cope with life. It is usually a mixture of mental health problems (long term and short term), some form of non-neurotypical mental disability (or whatever the current PC thing is to describe it, things like autism seem to factor high in the perpetual homeless I know), substance abuse, family issues, ex-forces etc. They existed prior to the current government and I've no reason to believe they wouldn't continue to exist even if they were made millionaires tomorrow. They are vulnerable people for a variety of reasons.
Now that said, there are many that pass through the groups I work with that have fallen on hard times and certainly austerity hasn't helped. Is that entirely the fault of the Conservatives? I'm not sure. Lehman Brothers crashing (the trigger for the recession) certainly wasn't anything to do with them. Could they have handled things better? I don't know that either. Could the previous government have made life a little bit harder for those claiming benefits in the 90's so that the current government didn't crack down too far with their current measures? Again I don't know. However I don't think you can give this entirely to the current government to shoulder.
Remember too there are a much wider and more long lived issues such as the lack of social housing, the numbers of private landlords who wouldn't rent to people in vulnerable situations etc. Locally we've had grassroots movements creating tent cities in nearby towns and cities as safe places with heating, water, food etc for the homeless which are broken down and everyone evicted from because "they're unsightly" or they "attract crime" etc. All they really do is allow people to live in a little closer to normality and peace. That's not especially down to the national government, although I would love for them to create a law preventing councils for doing such actions.
This last month we've been bombarded with adverts on TV for things like Crisis at Christmas. It's a wonderful charity and an excellent goal. How many people have given, and then given themselves a pat on the back and felt they'd done enough? Perhaps some of the problems of homelessness are a problem with society as a wider concept. Look at the times the homeless have been attacked, even killed, when they've done nothing other than sleep. There was a homeless man a year or so ago who couldn't get out of his sleeping bag in time to prevent being kicked almost to death. If he'd have got out of his bag, I promise you he'd have flattened the entire group that attacked him (he was ex military, I forget which branch now but seriously a fit and very strong person). Yes (I hope) those folks who view the homeless as vermin, lower than the low etc are few and far between but sadly they exist in this society, and I'm not sure there is anything the government can really do to stop that. But as a society perhaps we can. Perhaps we can take a stand against people in our circle who express hate towards those on the streets instead of doing the British thing of not getting involved.
I'll stand down off my soap box now. =)