How Many Council Houses Should Labour Plan to Build?

Red Brick blog asks how many Council houses should Labour plan to build?  In discussing the calls of a new campaign group, it asks the sensible question: "Do they really expect an incoming Labour chancellor to set a housing budget which is five times its current level and to be able to spend it from virtually a standing start?".

As we get closer to a General Election asking about the deliverability of Labour promises becomes more important.  If only because the electorate will need to believe the credibility of the promises that the Labour Party makes if it is going to vote for them.   That is not just about money.  It also involves trade offs around types of tenure, size of unit, availability of land and political resistance (sometimes from Labour's own councillors).

I am unsure how far the Party is prepared for these kind of questions.