One in five workers forced to self-isolate and unable to work from home received no sick pay or wages, the TUC has revealed.
It demanded extra help for people who cannot work from home but are ordered into quarantine to help curb the spread of coronavirus.
Currently they can receive a one-off £500 payment.
A survey of 2,200 people found a fifth (20%) of workers who have been forced to self-isolate, but unable to work at home, have received no sick pay (or wages) at all.
It also found two in five workers feared they would have to go into debt or arrears on their bills if their income dropped to £96 a week – the current level of statutory sick pay.
TUC general secretary Frances O’Grady said: “The Government must do everything possible to slow down the spiralling rise in Covid-19 cases.
“With the virus becoming more infectious, it’s more important than ever that people self-isolate when they develop symptoms.
“But the lack of decent sick pay is undermining Britain’s public health effort and is forcing workers to choose between doing the right thing and being plunged into hardship.
“Ministers must stop turning a blind eye to this problem and raise sick pay to at least the Real Living Wage of £320 a week, and they must ensure that everyone has access to it.”
By law, people must shut themselves away if they are “pinged” by the NHS test and Trace app as having come into close contact with someone who tests positive or they test positive themselves.
They should also self-isolate if they have any symptoms of the disease, are waiting for a coronavirus test result, if someone they live with has symptoms or tests positive, or if someone in their support bubble has symptoms or has tested positive.
The TUC also called for an overhaul of outdated workplace safety rules to protect essential workers.
Guidance for employers have not been fully updated since March 2020 – despite advances in the scientific understanding of the virus.
Transmission of Covid-19 is now understood to be mainly through infectious aerosols suspended in the air, rather than contact, which may mean protective measures are inadequate.
“Too many workers are still in indoor spaces without adequate ventilation, or proper social distancing from other staff or customers,” Ms O’Grady said.
“The government must update the rules on ventilation, masks, limits on numbers and social distancing in workplaces.
“Nobody should be put at unnecessary risk because safety policy is behind the science, and unfit to cope with new Covid-19 strains.”
On self isolation, a Government spokesman said: “There is a comprehensive package of financial support in place for workers who need to self-isolate to help stop the spread of coronavirus – including a £500 payment for those on the lowest incomes who have been contacted by NHS Test and Trace.
“Many employers pay more than the minimum level of statutory sick pay and employers with up to 250 staff can be reimbursed the cost of up to a fortnight’s statutory sick pay.”