In September last year, the government body published new household projections based on 2016 figures, to supplant the previous 2014-based projections.
However, when applied to the government’s new standard method, the 2016-based figures produced a much lower level of housing need, totalling 210,000 homes a year across England, far short of the government’s 300,000 units-per-year target.
Analysis by consultancy Bidwells showed that 17 local authorities would see their housing need levels fall by more than 50 per cent and 73 by more than a third. Cambridge, Oxford and Blackpool were among the areas projected to see real-term reductions in households.
Former housing minister Kit Malthouse said last Autumn that the 2016-based figures had produced "crazy" results.
As a result, the Ministry of Housing, Communities and Local Government (MHCLG) changed its Planning Practice Guidance (PPG) to make clear that planning authorities should use the older 2014-based projections for the standard method.
Last September's publication marked the first time the ONS produced the household projection figures, which were previously drawn up and published by the MHCLG.
Now, the ONS has published an analysis defending its 2016-based projections.
The body concluded that the 2016-based household projections "incorporate updated input data and include methodological improvements".
It said the differences between the 2014-based and 2016-based household projections "can be attributed to a combination of the updated input data (subnational population projections, revised mid-year population estimates and prisoner counts) and methodological changes implemented in the 2016-based methodology".
Among the methodological changes between the two sets of figures identified in the analysis, the ONS says the 2014-based projections used data from the 1971, 1981, 1991, 2001 and 2011 Censuses, supplemented by Labour Force Survey data. In contrast, the 2016-based projecions use data "from the 2001 and 2011 censuses only".
According to the ONS, the census years before 2001 used a different definition of the "household reference person" based on the oldest male, whereas the 2001 and the 2011 definition is based primarily on economic activity, "which makes these historical data less comparable".
Commenting on the ONS analysis, Jason Lowes, a partner in the planning team at consultancy Rapleys said: "There was somewhat of a furore about a year ago when the ONS published – for the first time having taken over the statistical responsibility from MHCLG – the 2016-based household projection figures.
"Given that [the ONS analysis] concludes that the difference between the 2014 and 2016 figures were as a result of methodological improvements informing the latter, the issue looks likely to be a continued bone of contention between local authorities, developers and the government.
"Notwithstanding this, at least for now the 2014-based figures look likely to be the first port of call for the majority of base-line housing need calculations."