One in 30 London children already lives in temporary accommodation, and this will only increase if we're not building the new homes for these families.
The reasons for the fall include rising construction costs, increased building safety costs (esp in London), and insufficient grant rates. Housing associations are also prioritising their own funds onto their existing stock.
It's also impractical from a financial perspective to build only social housing - the Government would need to put massive subsidy in (£100-£300k per home), which they clearly aren't going to do. So a lot of social housing is cross-subsidised via the building of market housing.
Social housing is the most direct way to help people in most acute need. But most of the population live in market housing - and we do need more of that too. (If we don't build enough market housing, that just pushes more people on the margins of affordability onto waiting lists for social housing)
Yes, the inclusion of children (who never occupy a home of their own) is part of the issue. Plus more older people who chose to live alone - we can't go evicting them and making them share their homes.
My best guess is that she's talking largely to the over 60s, who will have reared their own children when maternity pay was pretty much nonexistent so may be amenable to thinking "why can't the snowflakes support their own families just like we did?"
Exactly - housing quality and numbers aren't in any way a substitute for each other. Other people having nicer houses doesn't exactly help if you don't have one!
The number of people per dwelling fell in the late 20th century as the size of families fell and housing conditions improved. In the last 25 years it's been static, BUT the number of older people living 1-2 to a dwelling has grown. So they're are many more (would-be) households per dwelling.