UPDATE: This article has been updated with more information on housing association builds and the timeframe in question.
The lack of affordable housing is a chronic problem - on this, all the political parties are agreed. But when it comes to understanding the cause of the crisis, there's no such consensus.
While Labour has promised that it would double the rate of housebuilding by 2020 (equivalent to some 240,000 homes per year), one of its London Assembly members has argued that the party should "apologise" for its record on affordable housing.
Tom Copley, Labour's housing spokesman in the capital, said that Margaret Thatcher's government had built more council flats and houses in a single year than New Labour's managed in its entire period in office.
This is correct. The official data shows that the Blair and Brown governments built 7,870 council houses (local authority tenure) over the course of 13 years. (If we don't include 2010 - the year when David Cameron became PM - this number drops to 6,510.) Mr Copley has contrasted this figure with the record of Mrs Thatcher's government, which never built fewer than 17,710 homes in a year.
Between 1997 and 2010, of the 2.61 million homes constructed, only 0.3% were local authority tenure. Mrs Thatcher's government supervised the building of a similar number of houses (2.63 million), but 18.9% were LA or 'council' properties.
To look at it another way, New Labour built an average of 562 council houses per year. And Mrs Thatcher's Conservatives? 41,343. That said, it's also true that the number of council houses under construction declined steadily during Mrs Thatcher's era.
While the Conservatives have traced the shortage of affordable housing back to 1997, in fact the number of new council homes began to flatline shortly after Sir John Major succeeded Mrs Thatcher as Conservative PM.
However while Tom Copley talks specifically about council-built accommodation, we should also consider the homes built and managed by housing associations. These 'social landlords' provide affordable housing to those on low incomes, and were responsible for an increasing proportion of social house building from the early 1990s onwards. Between 1997 and 2010, some 350,000 housing association dwellings were built. If we look at both housing association homes and council houses, Labour built more affordable properties in 2009 than the Conservatives did in each year between 1987 and 1990.
On this front, the Coalition government is now following their lead. There has also been a slight uptick in the number of local authority homes under construction. However, it looks very unlikely that we'll be returning to the days when government was building tens of thousands of homes, rather than tens of hundreds, any time soon.