A freedom of information request by the Scottish Liberal Democrats said that total spending on the Scottish census was £135m, with a further £5m estimated to be spent over the next two financial years.

In comparison, the 2011 census cost £63.5m, and the 2022 census was the first Scottish census to be carried out separately to the rest of the UK.

The 2022 census was originally due to be held in 2021, but was delayed a year and run online due to the Covid-19 pandemic.

According to figures from the National Records of Scotland, which runs the census, the census had an 89% return rate, after an initial return rate for the 2022 census of 79% saw it extended by a month at an estimated cost of £6m.

Audit Scotland, which released a report last year calling for an investigation into the poor return rate in Scotland, said the original target had been at least 90% to ensure the census data could be used to produce the most accurate population statistics.

The English and Welsh census in 2021, which was carried out during Covid-19 restrictions, had a return rate of 97%, while the census in Northern Ireland also saw a return rate of 97%.

The Registrar General for Scotland established an independent group of census and data specialists said the data was sufficient to progress to the next stage of the census, involving an additional survey and drawing on administrative data such as the electoral register.

However, the low response rate meant the National Record of Scotland was more reliant on the use of administrative data than planned, according to Audit Scotland.

Data from the census is used to inform planning and guide public spending decisions for the next 10 years.  

An evaluation of Scotland’s 2022 census, with a focus on lessons learned, will be prepared for ministers and provided to parliament by the end of 2024.

Willie Rennie, MSP for North East Fife, said: “Ministers made significant changes including moving the census online and getting out of sync with data collection elsewhere in the UK. Then they refused to learn any lessons out of nationalistic belligerence.

“What’s even worse is that botching the census will now have a knock-on effect on the delivery of government services for the next decade. The cabinet secretary in charge needs to set out what kind of review of the census process will be done and how the government will ensure that these errors are not repeated.”

A National Records of Scotland spokesperson said: “Estimates from censuses elsewhere have shown that every £1 spent on census returns around £5 in economic benefit. While much of the costs of the census are focused on key delivery years, most long-term benefits are felt throughout the extended programme life cycle, after the collection phases.

“NRS has continued to ensure we only spend what we need to deliver a census and its associated benefits. Where efficiencies can be made, they have been to ensure we maintain value for public money.”