Everyone except MPs will have to wear face coverings while on the parliamentary estate due to rising Covid-19 cases, the House of Commons has ordered.
The measure will apply to staff, contractors and visitors but the Commons authorities said it could not compel MPs to wear masks as they are not deemed to be Parliament employees.
However, officials said Speaker Sir Lindsay Hoyle would be encouraging elected representatives, despite not being obliged to wear a face covering, to put one on in the Commons chamber unless they are speaking or are exempt.
A Commons spokesman said: “The House’s priority is to ensure that those on the estate are safe while business is facilitated.
“Due to recent increases in Covid-19 across the country, which are also being reflected in Parliament, we have updated our Covid-19 guidance for those working on the estate.
“Face coverings are now mandatory for all staff, contractors and third parties while on the estate, unless there is a legitimate exemption in place.”
The ruling comes after MPs were urged to wear masks during the Chancellor’s Budget speech on Wednesday by a coronavirus expert from the World Health Organisation (WHO).
Dr David Nabarro, the WHO’s special envoy for Covid-19, said that “everybody” should be wearing masks in close confinement with other people, “including our leaders”.
Health Secretary Sajid Javid has already committed to wearing a mask in the Commons when it is packed on Budget day, having urged politicians to lead by example following a recent spike in cases.
But Mr Javid said on Monday that wearing a mask in the crowded chamber is a “personal decision” for ministers and backbenchers.
Commons Leader Jacob Rees-Mogg last week insisted Tories do not need to wear masks in Parliament because with their “convivial, fraternal spirit” they know each other well.