The trustees for KPNQwest have said they will shut down the pan-European telco's network unless its customers cough up the money they owe by Monday.
The ultimatum was issued yesterday as part of rescue deal that, if successful, would keep the network running until the end of the month.
That would then buy enough time for KPNQwest's customers to find alternative network suppliers.
For the proposal to succeed it would require "substantial support" from all parties, including customers, suppliers and employees, the trustees said in a statement.
They added: "Should inadequate funding be received prior to the commencement of the plan at the close of business on Monday June 10, the network will be shut down, and all monies received will be reimbursed in full."
This latest development in the collapse of KPNQwest has raised concerns that if its network is shut down it could spell disaster for European Internet users.
It's estimated that KPNQWest's network carries between a third and half of all Internet traffic.
Today's Sun reports that millions of British internet users face a huge slowdown in their service next week because of the problems at KPNQwest.
The newspaper claims that the Internet could face a "meltdown" and warns that two of the UK's biggest ISPs - Freeserve and AOL UK - could be hit.
Responding to the article headlined 'Internet Heads for Meltdown', Freeserve said: "Freeserve's Internet service does not use KPNQwest's network, as reported. Freeserve uses the Energis network, and its service to customers will not be affected by what has happened to KPNQwest."
And a spokeswoman for AOL UK also dismissed the report adding that that while KPNQwest is a supplier, it is "only one of many".
"We are aware of the difficulties [facing KPNQwest] and we already have contingency plans in place.
"We foresee no disruption in the UK," she said. ®