the system of social housing in this country is a mess. it has been since thatcher sold off council houses and subsequent Labour, Conservative and con/lib governments have done nothing to sort it out. Labour had power for enough years to sort it but they didn't so I just don't buy the usual - its the tories nonsense.
there are so many problems with it , its hard to know where to begin. if you put up rents to the market rate then you will probably be increasing the amount of subsidy paid. recycling money that actually also means that you take out a chunk for "admin". if you keep rents lower than market rents then it skews the market - demand will always outstrip the ability to supply because everyone wants to pay less for housing if possible.
the problem at the moment is house blocking. People who started off low earners then became high earners and wont move on and people who live in houses larger than they need effectively stopping them going to families.
I always thought the answer to social housing lay in part with the old Peabody trust model. you rent your house or flat at below market rent on proof of income. every year you are required to give proof of income. once you start earning over a set % of average earnings you are given 12 months notice.
similarly if you move in as a family of 6 and the children leave home you are given a year to trade down to something smaller.
I get that people don't necessarily want to move house according to their income or circumstances but just as no one has a job for life any more no one should have social housing for life any more.
when we start using the stock that we have more efficiently and effectively then we can really determine if more needs to be built or not.
as for asking landlords to charge less that is bonkers. no one in their right mind is going to reduce prices for an asset and its supply and demand.