The firm which bought Thomas Cook shops has said up to 878 employees out of 4,500 may lose their jobs because of new coronavirus travel restrictions.
Hays Travel took on more than 2,000 former Thomas Cook employees when it went bust in October last year.
Owners John and Irene Hays said Spanish travel restrictions meant hundreds of thousands of holidays were cancelled.
They were "devastated" staff would lose jobs "through no fault of their own", the couple said.
In a joint statement, the Hays said they had "made every possible effort" to protect the jobs of all the firm's staff, "including those who were employed when Hays Travel took on the Thomas Cook shops last October".
The Sunderland-based company said it was now consulting with 344 staff training as travel consultants and the 534 who work in the foreign exchange division.
The firm said its experienced travel sales staff, apprentices and other head office staff were not affected by the cuts.
'No choice'
"We are devastated that after all of our efforts and the huge investment we've made, we now face losing some of our valued employees, through no fault of their own.
"Following the decision to ban travel to Spain and the changes in furlough conditions coming at the same time, we have had no choice," the firm added.
In July, the government brought back a 14-day quarantine for travellers returning to the UK from Spain after a spike in coronavirus cases.
The Foreign Office later updated its advice against all non-essential travel to Spain to include the Balearic and Canary Islands as well as the mainland.
And firms who have furloughed staff during the pandemic had to start contributing to the government job retention scheme from Saturday, putting more pressure on struggling companies.
Mrs Hays told the BBC it was "impossible to overstate the importance of Spain" on the company's business.
Mr Hays said the firm disagreed with the government's approach to quarantining Spain: "Other parts of Spain, on the Costa Del Sol, the islands, Majorca, Tenerife, Lanzarote, Ibiza, the Canaries... the incidence of the virus is very low - less than the UK.
"The German government's reaction has been to quarantine people going to the north-east of Spain, but allow people to go to all of the other places I've just said, and that's a much more targeted and sophisticated approach."
Hays Travel said it had a two-year turnaround plan in place, and that although 2020 "looked really bad", bookings for 2021 were already up on the same period in 2019.
