Frances O'Grady, head of the TUC, urged ministers not to "throw away" the good work of the jobs retention scheme, which has ensured millions of people have continued to be paid during the pandemic while being temporarily laid off from work.
But many now face a cliff edge at the end of October when the scheme is set to come to an end.
Chancellor Rishi Sunak has argued it would be wrong to keep extending furlough and give people false security that they are going to have a job to return to but Ms O'Grady insists it is too soon to withdraw support completely.
The TUC is proposing a short-term jobs scheme, which would involve workers whose jobs are at risk to spend time training for new roles while still being paid, to give them the best possible chance of finding new work quickly.
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It is also calling for the Government to boost statutory sick pay. The body says the Test and Trace system otherwise risks being undermined as people asked to self-isolate are forced to choose between staying at home or putting food on the table.
Ms O'Grady told the Star: "By any measure I think this scheme has certainly helped millions of workers, thousands of firms get back on their feet but it's too soon to pull the plug
"What we're arguing for is a new phase, a job protection and upskilling programme so that employers must bring workers back at least part-time. For any time that workers aren't at work we must have training and upskilling in place and that will be a good investment for the future, and ensuring in the same way as the first scheme workers get 80 per cent of their pay.
"It can't just be a blank cheque for businesses. They have got to come up with a clear plan to protect jobs and skills."
Ms O'Grady countered growing claims that Government support can't go on forever by saying withdrawing help too soon could do irreparable damage. She also pointed to other European countries who have pledged long-term help.
"The price of standing on the sidelines and watching jobs and good firms go to the wall is far higher than investing now to help them through this. All the evidence is that wage subsidy schemes help firms bounce back quicker."
She continued: "The only way we're going to get out of this crisis is to work our way out and grow our way out. That's the fact. It is worth looking at what other countries are doing.
"We've said support should be extended for at least six months. Look at France, Germany, Austria, they're extending their schemes for a year and in some cases until 2022 to provide certainty, so we're not the only country which is facing this challenge and what we're seeing from other countries is that they are in it for the long haul.
"They know the cost of mass unemployment ends up being much higher, damages our economy much more than acting now to protect jobs.
"We're not saying everything has to stay the same but there are an awful lot of decent companies and good jobs that risk going to the wall if the Government sits on its hands."
While mass unemployment is a likely outcome of the pandemic, the TUC boss insisted there is an onus on the Government to do everything in its power to mitigate the damage and save as many jobs as possible.
She said: ""I think it's the biggest threat we face and it's incumbent on all of us to do everything we can to stop it. We know who ends up paying the price of unemployment, it's ordinary working families.
"We need to make sure we support those jobs and companies which do have a viable future, targeted support for industries and we need investment for the future."
Ms O'Grady insisted adequate sick pay was crucial to helping stop the spread of coronavirus, to ensure those who are told to stay at home are comfortable enough financially to do so.
"It's the difference between being asked to do the right thing when asked to self-isolate or not because in the end people also have to feed their families," she said.
"So we're very clear, the Government's top priority has got to be sorting out that Test and Trace system but it's also got to recognise even if it was world beating, if you haven't got adequate sick pay you put people in an impossible moral dilemma.
"To make it work you've got to make it affordable for people to do the right thing."