The real issue is lack of houses, not tax credits, or anything else.
Lack of houses is keeping house prices and rents artificially high, and therefore driving the need for in-work benefits.
We've needed more houses for two generations. The fact we still haven't got even a tenth of what is needed tells us that it's a political problem pure and simple. With a main problem being it doesn't suit those in power, nor those that voted for them to see more (and therefore) cheaper houses.
I note, with interest, that every "initiative" to "solve the housing crisis" has avoided building new houses at all costs.
None of this should be news, or secret. Looking at local housing developments recently, I was told by the salesperson how the "stock" was being built - and sold - in phases to ensure the prices remained stable. Or, to put it another way, "rationed".
So, if developers are allowed to dick around rationing housebuilding, then we have to ask (a) if there is a housing crisis,and (b) if there is, why nothing is being done (talked about, yes. Done ? No.).
But then what would you expect from a government whose response to looming energy shortages is to dick around with "smart meters" rather than build new power stations ?