Keir Starmer has been urged to hike sick pay by unions representing millions of teachers, doctors, and railway workers.
In a letter to the PM,two dozen union chiefs said an increase is needed so "workers can meet the cost of living in their time of need".
Statutory Sick Pay currently stands at £116.75 - and will rise by just £2 in April next year. This is one the lowest levels among the 38 countries in the OECD group of nations.
In March a group of cross-party MPs said sick pay was failing to provide a "basic level of income protection" and should increase by £60-per-week to mirror Statutory Maternity Pay.
Those demanding action includes the British Medical Association (BMA), the National Education Union (NEU) and the Rail, Maritime and Transport (RMT) union.
They said: "We’ve heard of workers delaying their cancer treatment because on £116 a week they don’t know how they’ll be able to put food on the table.
"We’ve heard of workers struggling into work with a broken leg as they couldn't afford the bills. And we’ve heard of workers taking time off and getting into debt, having to leave the workforce or falling into destitution."
The union bosses added they were concerned "about the Government’s inaction on the low rate of Statutory Sick Pay".
But they welcomed Labour's commitments in the Employment Bill - spearheaded by Deputy PM Angela Rayner - such as ensuring sick pay is paid from day one. Under existing rules the payment is only available after three days of sick leave.
Amanda Walters, Director of the Safe Sick Pay campaign, said: “The Government’s plan to make sure employers pay sick pay from day one and extend it to low income workers is welcome, but we need a timeline for how they intend to increase the rate sick pay is paid at. Otherwise, sick pay remains too low to be safe for workers.”
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A Department for Work and Pensions spokesman said: “No one should be forced to choose between their health and financial hardship, which is why we have consulted on plans to strengthen Statutory Sick Pay and make sure everyone is entitled from the first day they are sick, regardless of earnings.
“That consultation closed this week and we’ll be considering responses at pace.
“These reforms as part of the Employment Rights Bill will support people managing a health condition to stay in work and raise living standards across the country.”