It comes as nearly one in four childcare providers in England could close in the next year, according to analysis from the Early Years Alliance childcare charity.
Labour analysis also found that costs of nurseries and childminders have risen around three times as fast as wages since the Tories took power in 2010.
Shadow education secretary Kate Green said: “The Conservatives have created a perfect storm for working parents across the country, with a crisis in the childcare sector locking children out of early education and making it impossible for many parents to return to work.
“Ordering parents back to work without allowing them to access the childcare they need is a stark reminder that Boris Johnson is completely out of touch with the needs of working families.”
The Department for Education said the sector had received “significant financial support” during the pandemic and will benefit from extra investment.
Labour’s warning comes as Mr Johnson encourages people to return to their workplaces if it is safe to do so to boost the economy after months of lockdown.
Nurseries closed their doors in March along with many businesses to slow the spread of Covid-19 and only remained open to vulnerable youngsters and the children of key workers.
But childcare providers have issued warnings over their financial viability, with rising costs and reduced capacity due to the pandemic.
Purnima Tanuku, chief executive of the National Day Nurseries Association charity, said greater funding is needed as the situation is “clearly not sustainable”.
She said: “Since lockdown, nurseries have also had to absorb additional operating costs such as installing more handwashing stations and extra cleaning. But as costs have increased, their income has dropped due to low numbers of children.
“The Government has given most local authorities an extra 8p this year per hour per child, but this won’t even cover inflation, let alone take account of above-inflation national minimum and living wage rises.”
A Department for Education spokeswoman said early years providers will benefit from £3.6 billion funding from next year for free early education and childcare places.
“This important sector has received significant financial support over the past months to provide stability and reassurance,” she added.
“We are continuing to provide extra security to nurseries and childminders that are open by ‘block-buying’ childcare places for the rest of this year at the level we would have funded before coronavirus – regardless of how many children are attending.”