Unions representing civil servants and parliamentary staff have written to the House of Commons Commission calling for better protections.
They say authorities must tell staff to walk away from “reckless” Members of Parliament who ditch their masks after the rules ease on Monday.
Bosses also said Sir Lindsay Hoyle, Speaker of the House of Commons and commission chair, must make it clear to MPs that staff will walk away if they show a “blatant disregard” for their wellbeing.
A number of MPs are expected to bin their face coverings in a bid to return to normal.
However, there are already reports of rising cases amongst those working on the Parliamentary estate.
It comes amid an ongoing row as MPs are “strongly encouraged” to continue wearing coverings in Parliament after July 19 but are not compelled to do so.
Meanwhile, all other staff on the Westminster estate are required to wear masks while moving around the premises.
The letter said: “If, as stated, the Commission cannot compel Members to adhere to the instruction on face coverings, then they must consider their obligations to protect staff who find themselves in a situation where they are in proximity to a Member who refuses to wear a face covering.
“A safe working environment is not a choice, it is an obligation. As such we believe the Commission should make clear to all House staff and Members that, in circumstances where a Member refuses to wear a face covering, the staff member is permitted to remove themselves from that environment, and this would be a reasonable action to undertake.”
The commission has been approached for comment.
A spokeswoman previously said the commission’s approach throughout the pandemic had been in response to and in line with Government regulations.
She added: “For the final four days before the House rises for the summer recess, Members are strongly encouraged to continue wearing face coverings.”
Dave Penman, General Secretary of the FDA union that represents civil servants, said the commission had a “duty of care to its staff”.
He added: “It cannot be right that the commission expects members of House staff to be put in harm’s way by working in close proximity to MPs who refuse to wear a face covering.
“If MPs cannot be compelled to comply with these rules, then the Commission must ensure that House staff are not put at risk by instructing them to immediately leave any enclosed area where this occurs.
“The Speaker should make clear to MPs that this will be the consequence of their actions if they ignore the rules and show blatant disregard for the wellbeing of staff.”
The FDA union has already threatened to “name and shame” MPs who refuse to wear face coverings in Parliament when restrictions are lifted.
MPs have four more working days in Parliament before they break for summer recess on Thursday.
Leader of the Commons Jacob Rees-Mogg suggested he would no longer wear his mask around the Parliamentary estate from Monday.
“This morning I wandered around the palace of Westminster wearing a mask, and met almost nobody in those circumstances. I will not be wearing a mask – what would be the point?” the Cabinet minister told ConservativeHome earlier this week.
A House of Commons Commission spokesperson said: “The House of Commons Commission has received further representation from Parliament’s unions regarding the wearing of face masks in the House of Commons.
“Our priority is to ensure a safe and functioning Parliament in line with Government regulations.
“We hope that numbers on the Parliamentary Estate will remain limited next week and that all passholders will continue to exercise caution as we enter step 4. We will, of course, monitor the situation from day to day.”