Prospects for saving travel giant Thomas Cook are slim, according to sources.
Crucial talks aimed at preventing the holiday firm going out of business were held throughout Sunday amid fears that tens of thousands of holidaymakers will be stranded.
Unions representing Thomas Cook staff have urged the Government to intervene.
Foreign Secretary Dominic Raab has assured the firm’s worried customers that contingency planning is in place in the event the business cannot be saved.
Brian Strutton, general secretary of the British Airline Pilots Association, said: “Thomas Cook staff are going through hell as their livelihoods are put on the line; they have no idea if they will wake up tomorrow with a job or not.
“Their dignity in carrying on working for Thomas Cook customers under this pressure is a credit to them.”
Thomas Cook Group chief executive Dr Peter Fankhauser remained tight-lipped as he emerged from a day-long meeting on Sunday after negotiating with creditors in a final bid to save the firm.
He would not comment on whether a deal had been reached or if the firm would consider approaching the Government for a taxpayer-funded bailout.
He also refused to say anything to Thomas Cook’s customers as he walked out of the service exit of City law firm Latham & Watkins, in Bishopsgate, central London, surrounded by colleagues.
The Financial Times quoted two anonymous sources – one close to the negotiations and another involved in the restructuring deal – who said the rescue efforts were unlikely to succeed.
The travel company is on the brink of falling into administration unless it finds £200 million in extra funds, with the jobs of 22,000 staff worldwide at stake, including 9,000 in the UK.
Mr Raab tried to quell fears the collapse would leave up to 150,000 UK holidaymakers stranded abroad, insisting contingency planning is place.
Thomas Cook reassured customers on Sunday that their flights and holidays are operating as normal and that “we are working on recapitalisation plans”.
But many, including couples planning to get married abroad, were left in limbo, not knowing whether their holidays will still go ahead.
Lorna Clark, 33, and her fiance, Paul Ruckledge, who is in his 40s, are due to fly from Manchester to Paphos, Cyprus on September 30.
Ms Clark’s sister-in-law Sarah Cooper, 35, said: “She’s just in an absolute panic. There’s nothing we can do until we find out for definite if they’ve gone bust. It’s just horrendous really.”
Thomas Cook said it would not be sending any more tourists to the Les Orangers beach resort in the town of Hammamet, near Tunis, after complaints the hotel was refusing to let guests leave while demanding extra money.
Ryan Farmer, from Leicestershire, told BBC Radio Five’s Stephen Nolan the hotel had on Saturday afternoon summoned all guests who were due to leave to go to reception “to pay additional fees, obviously because of the situation with Thomas Cook”.
With many tourists refusing to pay on the grounds they had already paid, security guards were keeping the hotel’s gates shut, refusing to allow guests out, or let new visitors enter.
“We can’t leave the hotel. I’d describe it as exactly the same as being held hostage,” Mr Farmer said.
Thomas Cook told one customer on Twitter: “A small number of customers were asked to pay for their hotel room before leaving Les Orangers in Tunisia yesterday, we have refunded those customers who paid on their credit cards.”
The Transport Salaried Staffs Association (TSSA), which represents workers at the company, said the Government should be ready to assist with “real financial support”.
General secretary Manuel Cortes called for the Government to reveal how much it is prepared to spend repatriating thousands of Thomas Cook holidaymakers.
It is understood that Thomas Cook has approached the Government in an attempt to plug a gap in its funding.
A Government spokesman said: “We recognise it’s a worrying time for holidaymakers and employees.
“The financial circumstances of individual businesses are a commercial matter, but the Government and the Civil Aviation Authority are monitoring the situation closely.”
Unite accused the Government of leaving workers and customers “high and dry” while landing taxpayers with a bill for hundreds of millions of pounds.
Unite represents nearly 3,000 cabin crew and engineers at Thomas Cook’s airline.
General secretary Len McCluskey said: “News of the needless collapse of Thomas Cook is devastating for the workforce and customers. Thomas Cook Airlines was a profitable and viable operation with a loyal workforce.
“Instead of stepping in and giving Thomas Cook the breathing space it needed to restructure its finances, the Government’s ‘do nothing’ attitude has left workers and customers high and dry while landing taxpayers with a bill of hundreds of millions of pounds.
“Unite will be meeting the administrator and giving our members maximum support while working to match Thomas Cook Airline workers with other airlines that have vacancies.
“Unite will also be launching legal action on behalf of our members over a failure to consult on the redundancies that have resulted from the firm’s collapse.”