Well, of course it could happen. Could is not the same as would but if the question is theoretically could it? Then the answer has to be yes, it could. It would be quite simple actually if a party actually wanted to do it.
if you wanted to bring back the workhouses, how would you go about it?
well, you'd begin with a campaign that would serve to dehumanise the group you were targeting. In this day and age that is best served by heavily edited tv programmes that appear to show them as despicable people leeching off the Hard Working Man. Add stories about people with 20 kids claiming thousands in benefits and finish off with lots of stories of faking disabilities and flat screen tvs and you have a population that views a segment of society as a problem to deal with
Then you get yourself a set of policies to 'help' them. Maybe you want to get them back into work, so you start work experience for them, where they go work for, for example, tesco or something, for their benefits.
Then you'd change that from voluntary to compulsory, all in the name of helping them back into work. If they didn't want to do it, then they'd have their benefits stopped.
Next, you'd want to get them into the housing so you'd run voluntary residential programmes for long term unemployed, where they'd live in at a centre for a period, learning vital job skills with the aim of helping them back into employment.
Then you'd add the compulsory work placements or lose your benefits to the residential scheme and you'd have - live in this place and learn these skills or lose your benefits.
Then you'd convince the rest of the population that it was in these people's best interests to live in, because you're helping them. Plus they aren't on the streets and isn't it nicer.
Then you'd have a subtle shift in policy that meant they were not allowed to leave until or unless they had a job. You'd say it was for their benefit and you are only trying to help them. The rest of the population would have watched enough programmes to know what a problem they are and be right behind you.
That's how it could be done.
Whether it would be done is another matter and everyone has their own view on that.