@GETTINGLIKEMYMOTHER is right - a private rental market is neccessary, but needs to be better regulated. Social housing is also important - and the sell-off of council houses is responsible for a lot of the current problems IMO. We were told that the income from selling council houses would fund the building of new ones, but I remember hearing the statistics a few years ago, and only a fraction of the sold-off houses have been replaced - which is an outrage.
But social housing on its own won't meet all the needs of the rental market - the students who need a house/flat for a year, for example, or people who are moving and need somewhere for a few months - when we moved from Essex to Scotland, we rented for six months, in the area we wanted to live in, so we could look for a house to buy without having to travel hundreds of miles to viewings. It meant we could learn more about the area, and where we'd want to live, in a way that would have been much harder, long distance.
I have watched all the series of Nightmare Tenants, Slum Landlords - and there are clearly arseholes on both sides - tenants who trash properties or default on thousands of pounds in rent, and landlords who are only in it for profit, and who treat their tenants appallingly. I suspect both groups are in the minority - but I also think that landlords have a fair amount of protection in law already and maybe the rights of tenants need to be made better.
Of course, this is just speculation on my part - it's a long time since I rented anywhere, so my experience isn't that relevant. Even the Scotland move rental was over 10 years ago! I was in rented shared houses as a student nurse, as a nurse and then again as a student when I went to Uni - my landlords were all OK, even though I was mainly renting at the lower end of the market - and I like to think I was a reasonable tenant - paid on time and treated the property with respect.