Working parents trying to balance work and childcare should be put on furlough while schools are closed, the umbrella body for UK trades unions says.
Bosses may not be aware that they can use the scheme to support parents, according to the Trades Union Congress.
Employers must “do the right thing and furlough mums and dads”, the TUC said.
All secondary schools will remain closed to students this week, except for the children of key workers such as NHS staff. Students are expected to return on a staggered basis from 11 January.
Most primary schools are open to pupils from Monday, except in London and parts of the south east of England where the spread of a new, more infectious, strain of coronavirus is already high.
However, decisions over whether it was safe for pupils to return to school in person were still being discussed over the New Year holiday weekend, leaving parents with little time to find support.
“Without further action, many will have no choice but to cut their hours or take unpaid leave from work,” said Frances Grady, general secretary of the TUC. “This will lead to further hardship and will hit mums and single parents hardest.”
The TUC said its research showed that in March, when schools were closed during the first period of lockdown, one in six mothers reduced their working hours due to school and nursery closures. It said single parents were also more likely to be affected.
Self-employed parents should also be given support through access to the self-employed income support scheme, the TUC said. It is calling for employees to be given a right to paid parental leave and flexible working beyond the current crisis.
One of the arguments for keeping schools open, rather than switching to remote learning, is to allow parents to continue to work.
However, there is a growing debate over whether the new coronavirus strain, which is significantly more infectious than the original strain of the virus, can be contained without closing schools for longer.
While cases of the virus are increasing in almost all age groups, the percentage testing positive is highest among secondary school age children, according to the Office for National Statistics. While schools practice social distancing where possible, students continue to mix with others within their bubbles.
“The health and safety of school staff, children and parents and the wider community must come first,” said Ms O’Grady.
Boris Johnson, interviewed on the BBC’s Andrew Marr show on Sunday, said there was “no doubt in [his] mind that schools are safe”. But the prime minister did not rule out further closures.
Teaching unions have told staff at primary schools it is unsafe to return to work and are calling for remote learning to be introduced across all primary schools. Some local authorities have also expressed concerns.
A government spokesperson said it would be “socially responsible” for employers to take account of a person’s childcare responsibilities and individual circumstances.