Around 680 staff have been made redundant at window and door manufacturer and seller Safestyle.
The business has gone into administration and the GMB union had expected up to 600 job losses.
But on Monday, administrators Interpath Advisory said the number of redundancies was about 680.
Only 70 of the roughly 750 staff have been retained.
Customers with outstanding Safestyle orders will not have them fulfilled, Interpath Partners said.
If a buyer is found for parts of the business, customers may be entitled to have their orders completed by the new owner.
If this happens, Interpath said it would post it on the Safestyle website and its own insolvency portal.
Staff were unexpectedly texted to “down tools” on Friday evening and received news of the appointment of administrators on Monday in the car park of the company’s headquarters in Bradford, GMB said.
“Loyal Safestyle UK workers have been treated absolutely abysmally,” the union said.
“They’ve been made redundant with immediate effect and told they won’t get another penny from the company.”
GMB organiser Bob McNeill added: “Bosses didn’t even have the decency to let them into the building out of the pouring rain
“Safestyle received millions of pounds of orders last month – where has that money gone? GMB will not stop fighting until these members get the money they’re owed.”
Employees worked at a factory in Wombwell, near Barnsley, and in 42 sales branches and installation depots across the UK.
Blamed for the wind down was high cost inflation, ongoing economic uncertainty and fragile consumer confidence.
These pressures were exacerbated by an “unseasonably warm September, which has dampened customer demand”.
“These are really challenging times for companies across the home improvement market,” said Rick Harrison, managing director at Interpath Advisory.
“After seeing strong sales during the COVID-19 lockdown periods, many companies are seeing trading being impacted by the cost-of-living crisis and soaring costs.”
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On Friday, the Safestyle board filed a notice of intention to appoint administrators and said the company could not continue trading as a going concern.
Trading in company shares on Friday morning was temporarily suspended, “pending clarification of the company’s financial position”, a regulatory notice said.
Additional funds had been sought but on Thursday, the company said it did not expect to be in receipt of capital or new financing.
A buyer for Safestyle was also sought but despite interest from “a number of parties”, the administrators said “a solvent solution was unable to be found”.
