The PCS, the Civil Service’s largest union, said many members were already willing to spend more than 40pc of their working week in the office.

However, it claimed that mandatory attendance “robbed” staff of flexibility to manage childcare and other domestic responsibilities, while also forcing them to make “unnecessary” office commutes.

The ONS workers are based across Britain, in offices including London, Manchester and Edinburgh.

The PCS previously argued that many workers only accepted a job at the agency because of its home working policy.

An ONS spokesman said it has “robust plans in place and does not anticipate any disruption to key ONS publications”.

It said it firmly believed that a reasonable level of office attendance was in the best interest of the organisation and its colleagues.

“Face-to-face interaction supports personal collaboration, learning and innovation,” it said.