Masks are being made mandatory again for all parliamentary staffers – but not MPs – amid concern over the recent rise in Covid cases and the safety of workers in the Palace of Westminster.

It is the first reintroduction of measures by the parliamentary authorities since restrictions were relaxed over the summer. Those who refuse to wear a face covering will be told they must leave the estate.

New guidance was issued on Tuesday in advance of Rishi Sunak’s budget speech on Wednesday. It said that “all face-to-face meetings with colleagues should be avoided, unless there is a business need” and people should “space out and avoid sitting directly opposite each other in working areas [to] avoid close contact at all times”.

However, MPs cannot be forced to follow the same rules, so those who choose to continue following the law rather than the advice are free to do so.

Many Conservatives have been seen recently packed shoulder-to-shoulder in the Commons chamber, while Labour MPs have made a point of wearing masks.

Jacob Rees-Mogg, the Commons leader, last week appeared to joke that his party’s “convivial, fraternal spirit” meant they were acting in line with the government’s Covid guidance.

It came after Sajid Javid, the health secretary, said politicians have a responsibility to set an example in the battle against Covid, including wearing masks in crowded spaces.

Tory MPs have since been told by senior party figures to wear masks for Wednesday’s budget as it will be watched by thousands of people, and ministers have realised they need to set a better example to encourage mask-wearing.

A memo sent to parliamentary staffers and contractors said the change was “due to recent increases in Covid-19 across the country, which are also being reflected in parliament” and added “we are aware some of this guidance alters changes only recently agreed” but that the situation was “highly fluid”. It will be reviewed on 4 November.

A staffer said of the rule change not applying to MPs: “It’s ridiculous that they’re being exempted from steps which will keep us all safe.”

Another one called it “utterly absurd”.