New census data on London’s population figures should be treated with “extreme caution”, according to boroughs in the capital.

Responding to the publication of the Census 2021 results, the cross-party group London Councils warns that the number of Londoners is likely to have been significantly undercounted – potentially having a major impact on future funding allocations for the capital’s public services if not adjusted for.

The census data suggests London’s total population in March 2021 was almost 300,000 (3%) lower than the Office for National Statistics’ (ONS) previous population projection for 2021, with some boroughs’ figures almost a quarter (24%) lower.

London Councils estimates around £4 billion of government funding to London local authorities relies directly or indirectly on census population figures. There will also be implications for billions of pounds of funding for the GLA, the NHS, police, fire and other much-needed frontline services.

The census was taken in March 2021, during the third national lockdown in response to the Covid-19 pandemic. Boroughs are concerned that at this time many of their residents – particularly students, young people on furlough, and migrant workers from abroad – may have temporarily relocated to family homes outside of the capital.

Highlighting additional longstanding challenges around accurately counting population in London due to the capital’s high rates of homelessness, language barriers, and digital exclusion, London Councils believes this combination of factors means the Census 2021 results are particularly problematic.

The umbrella body, which represents all 32 boroughs and the City of London Corporation, is calling on the ONS to ensure a rigorous statistical process to adjust for the temporary population dip caused by the pandemic when it produces its population estimates for 2021 and 2022 – which will be used in funding formulae for years to come.

London Councils is keen for an ongoing dialogue with ONS colleagues over these issues, including working together to sense-check against other administrative data sources, such as the Schools Census, and developing an accurate and robust approach to measuring a fast-changing population.

Cllr Georgia Gould, Chair of London Councils, said:

“Census 2021 took place during the extraordinary circumstances of the Covid-19 pandemic and a national lockdown, so this snapshot data must be treated with extreme caution.

“The census is a really important tool for policy and decision makers. Accurate census data matters for Londoners because it helps determine government funding allocations to local authorities. Billions of pounds for frontline services are at stake.

“Counting London’s diverse population is an incredible challenge even at the best of times due to our high levels of migration, homelessness and population churn. The lockdown will have undoubtedly made this worse, particularly for communities who suffer from digital exclusion.

“It’s a bitter irony that it’s often the Londoners with the lowest census response rates who most depend on local authority support – but even small inaccuracies in population counts can seriously undermine future service provision.

“We are concerned that, without looking at the data in the context of the challenges the pandemic created, Londoners will lose out.”

The census is vital for central and local government policy making and planning the delivery of public services. As well as underpinning the population estimates and projections that influence funding allocations, the census provides unequalled detail on population characteristics that help authorities tailor services to reflect residents’ needs.

It is estimated that one in ten London residents were missed by the count for the previous census in 2011. London Councils fears an even higher figure of missed Londoners in Census 2021.

The Covid-19 pandemic and national lockdown had a major impact on Census 2021 promotion work. The usual word-of-mouth communications routes were unavailable and public advertising will have been less effective as people spent more time indoors.

Boroughs repeatedly expressed concern at Census 2021’s emphasis on digital engagement, with most communications and support provided online rather than through face-to-face services or telephone support. London has extremely high rates of digital exclusion, with an estimated 270,000 Londoners completely offline and 2 million having low levels of digital engagement.