The situation in the UK and in Sweden appears to be very different, though. Sweden's rent control was certainly welcomed as pro-tenant policy, except (as noted by GP) has led to a black/secondary market of sub-letting and selling existing rent-controlled contracts at enormous prices, while keeping economical incentives for new construction low. That's really basic economic literacy and even suggested by OECD to the Swedish government. Of course, that doesn't stop eg Berlin leftist parties to suggest rent controls (read: to buy votes).