Lawyers have sent a letter before action on behalf of the federation, arguing that attempting to understand data on ethnic Sikhs using religious information would lead to inaccurate results.  

In the last census in 2011, around 430,000 Sikhs were recorded based on a non-mandatory question about religion. However, the federation argues that not everyone who identifies as ethnically Sikh would identify as Sikh by religion, and estimates there are 700,000 to 800,000 ethnic Sikhs in the UK.

The organisation claims that the process preceding the recommendation not to include a Sikh ethnicity category in the census was unlawful.

Rosa Curling, solicitor from law firm Leigh Day, said: “Our clients have identified a number of flaws within the process for determining whether to include a Sikh ethnicity category in the 2021 Census. They believe it is crucial that individuals are able to identify as ethnically Sikh in the next Census to ensure a more accurate picture of the community is taken.”

In its white paper outlining the census proposals, published in December 2018, the Office for National Statistics (ONS) said that it had found no evidence that religious and ethnic group questions were capturing different Sikh populations.

A spokesperson for the ONS said: “No group will be missed out in the digital-first 2021 Census. The ONS recommendations follow extensive research and consultation with groups and individuals and everyone who wishes to identify as Sikh will be able to do so. The religion question will have a specific Sikh tick box response option and everyone who wishes to identify as Sikh in response to the ethnicity question will be able to do so through a write-in option. We believe these proposals will enable public bodies to work with the Sikh community in shaping public services to meet their needs.”