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MPs “disenfranchised” by the government’s order to return to parliament would be able to sue on grounds of sex, age and disability discrimination in any other workplace, according to new legal advice.

Parliamentarians vulnerable to coronavirus – pregnant women, the over-70s, those with disabilities such as cerebral palsy or who suffer underlying health conditions – will lose out under the drive to return to work in person, a briefing note by Thomsons Solicitors warns.

Female MPs with particular childcare difficulties caused by the crisis are also likely to suffer discrimination under the plans.

The House of Commons is poised to return on Tuesday after its Whitsun recess, but without the remote voting and video participation in debates that were introduced at the height of the pandemic.

Commons leader Jacob Rees-Mogg scrapped the “hybrid” experiment in a bid to show that MPs were leading by example as the country began a phased exit from strict lockdown rules.

Commons speaker Sir Lindsay Hoyle is expected on Monday to publish his own safe guidelines for voting in person, with a long, socially distanced queue system rather than MPs squeezing into their narrow voting lobbies.

But Rees-Mogg is coming under cross-party pressure to allow some continuation of remote voting and working for parliamentarians forced to work from home.

Rob Halfon, the Tory chair of the education select committee, has a moderate form of cerebral palsy which makes it difficult for him to attend parliament during the pandemic. He has already warned that the plans would “disenfranchise” him and others.

A new legal note drafted by Thompsons – published in full by HuffPost UK (below) – sets out that in any other workplace the proposed removal of remote working would be classed as discriminatory on grounds of sex, age, disability and pregnancy under the Equalities Act and the Human Rights Act.

The briefing, commissioned by Labour, states that those MPs who are “clinically vulnerable” are all still advised under government guidance “to stay at home as much as possible”.

The discrimination would be both direct and indirect and “give rise to categories of MPs who would be likely to be placed at a disadvantage on grounds of disability, age, sex and/or pregnancy”, it said.

“It is, for example, entirely possible to predict that there are circumstances where an MP’s parents ordinarily provide childcare while the MP is in parliament, but are unable to do so now because of isolating, or shielding, requirements.”

Several female Tory MPs have already warned the government that they risk being “disenfranchised”, along with other colleagues who have to work from home, by the return to traditional arrangements for the Commons.

The Thompsons legal note states that if a “higher proportion of women than men amongst MPs had primary child caring responsibilities then, especially at a time when the majority of school year groups will remain closed for the foreseeable future, then women are likely to be disadvantaged by the envisaged return to parliament”.

“This may also arise where an alternative childcare provider should, following government guidance, isolate or shield,” it adds.

The note does make clear that the unique states of parliament means that in fact the government or Commons authorities would not be liable to legal action.

“If MPs were ‘employees’, then we think that the return of parliament currently envisaged by the government would be likely to amount to indirect discrimination on grounds of disability and/or age and/or sex and/or pregnancy under the Equality Act 2010 (‘EqA 2010’).

“But MPs are not employees and are not protected under the employment (or office holder) provisions of the EqA 2010; and the Human Rights Act (‘HRA’) does not assist.”

Ellie Reeves, the shadow solicitor general, said: “At this time of national crisis, parliament should be leading by example. The government’s guidance is clear: if you can work from home, stay at home.

“However, ministers are ploughing ahead with plans to abolish the arrangements for a virtual parliament.

“These proposals are not only a risk to public health, but they also discriminate against MPs who are having to shield from the coronavirus and cannot safely return to work as usual. The government has 48 hours to rethink its proposals and do the right thing.”

The idea of allowing some exemptions to continue remote voting is being considered by Rees-Mogg, although it is unlikely that MPs will still be allowed to take part in debates via Zoom video calls.

Former cabinet minister Theresa Villiers told the BBC’s Westminster Hour that while she supported the return to parliament, some exemptions could be made.

“Personally, I could happily live with electronic voting continuing for a period if there isn’t a workable alternative but I do think it’s important that MPs are back in their place of work. We’re encouraging others to do that.”

A government spokesperson said it was crucial for parliament to get back to delivering and scrutinising important legislation.

“Those who need to shield due to age or medical circumstances should continue to do so and informal arrangements, including pairing, will be in place to facilitate this.

“The House authorities have carried out a risk assessment of the Parliamentary estate to ensure it is a Covid-19 secure workplace in line with PHE [Public Health England] guidance.”

On Monday, Rees-Mogg published the government’s motion setting out that any MP who wants to vote must “participate physically within the parliamentary estate” and stick to Public Health England advice.

His spokesperson said: “The speaker will write to all MPs later today explaining how the House will vote on the government’s motion, which is expected to outline how future voting will take place.”

The Commons procedure committee warned last week that it had “serious concerns” over the return to traditional voting methods proposed by ministers.