A group of single parents who cannot claim welfare payments because of their migration status are suing the government.
A hearing at the High Court will hear pleas for the restrictions to be lifted due to the coronavirus outbreak.
Lawyers say tens of thousands of people are affected, mainly mothers from commonwealth countries with UK-born children, who work in low-paid jobs.
The Home Office said "nobody should find themselves starving or destitute".
Campaigners say the workers face an "impossible choice": Whether to continue working through the outbreak, putting themselves and others in danger, or stop working and have no means of paying for food, rent or bills.
'Not entitled to anything'
Single mother Zeenab, a carer who looks after adults with epilepsy, has had to reduce her hours to look after her seven-year-old son since schools were shut last month to help limit the spread of coronavirus.
As a key worker she is entitled to continuing childcare but her son's school said they can only provide two days a week.
She says she has been forced to cut her working hours from around 50 a week to just 12 and now takes home £300 a month after deductions and transport costs.
"I don't know what I'll do," she said.
"In a few weeks I won't have enough for food or rent and I'm really worried.
"I love my job. I'm hard working. I want to work and I pay taxes but I'm not entitled to anything."
The government has said workers affected by the coronavirus crisis should claim universal credit.
Since the outbreak began almost one million people have applied for the benefit.
But so-called "no recourse to public funds" rules attached to certain immigration statuses mean some are not entitled to state support.
Zeenab, originally from Sierra Leone, came to the UK in 2007 and gave birth to her son in 2012.
She has limited leave to remain and so cannot claim any state benefits like child allowance or universal credit.
She is now part of a group of single parents challenging the restrictions at the High Court on Friday.
If they succeed, the "no recourse to public funds" policy would be suspended, ahead of a full court hearing where the parents will argue that it should be permanently scrapped because it discriminates against women and ethnic minorities.
"The policy causes intense poverty at the best of times," said Caz Hattam, from the Unity Project, a volunteer-led organisation behind the legal challenge.
"But since the coronavirus outbreak, things have become desperate. We want an immediate suspension so these families can access basic welfare support during this crisis and, indeed, any future crisis."
Human rights lawyer Adam Hundt, who is representing the group, said: "These are the mothers of British children who have been working, paying in tax and national insurance and they're left with literally nothing and relying on charity.
"There's a huge cohort of British children who are not getting the same social safety net that my children would."
The Home Office said it would not comment on ongoing legal proceedings but a government spokesman said: "The government is supporting people through this crisis and nobody should find themselves starving or destitute.
"Measures we have brought forward, such as rent and mortgage protections, and food vouchers, are not considered public funds and can be accessed by those migrants with leave to remain who meet the eligibility criteria."