The threat of disruption to ONS services could have a significantly broader impact given the body’s role as the UK’s official statistical institute.
The ONS is responsible for producing monthly data on inflation, employment and GDP – all of which is closely watched by government officials and Bank of England rate-setters for signals of how well the economy is performing.
It also carries out a census of England and Wales every 10 years.
Staff at the ONS, who are based in the organisation’s Newport headquarters, as well as sites in London, Darlington in County Durham, Manchester, Edinburgh and Titchfield in Hampshire, have been told to spend at least 40pc of their time in the office.
This is below other government targets, which usually require civil servants to go into the office for at least 60pc of their contracted hours.
The PCS has previously argued that many workers are already meeting the 40pc target but that mandated attendance would reduce flexibility.
An ONS spokesman said: “We have robust plans in place and do not anticipate any disruption to key ONS publications.
“Nevertheless, we still believe firmly that a reasonable level of office attendance – in line with the wider civil service – is in the best interests of the ONS and of all our colleagues. Face-to-face interaction supports personal collaboration, learning and innovation.”