Tens of thousands of holidays to Turkey are being cancelled after the UK government added the country to the quarantine list on Thursday night, dashing hopes of a boost for the travel industry from late summer sun and October half-term breaks.

The announcement was tweeted by transport secretary Grant Shapps, stating that all arrivals into the UK from Turkey would need to self-isolate for 14 days from 4am on 3 October, along with Poland and the Caribbean islands of Bonaire, St Eustatius and Saba. Shapps justified the move by saying that the Turkish Health Ministry had been “defining the number of new Covid cases in a different way to the definition used by international organisations such as WHO and ECDC”.

Bookings for Turkey had seen a boost after other popular holiday destinations were added to the list last month, including several Greek islands and Portugal. Turkey had not been considered a likely contender for quarantine measures, given that yesterday’s reported case numbers were 12.9 per 100,000 over the previous seven days, significantly below the 20 per 100,000 the UK government regards as a criteria for quarantine.

There are an estimated 10,000 UK holiday makers in Turkey at the moment and a further 40-50,000 due to travel there in the next month, according to Paul Charles of travel consultancy the PC Agency. Tour operators have already begun cancelling large numbers of bookings.

Thomas Cook has removed holidays to Turkey (along with Poland) from sale. Customers can get a refund on trips, postpone or change destination. A spokesperson for Thomas Cook said that it was one of the most popular choices for holidays since the company relaunched last month, and that “only a handful have cancelled”.

TUI has cancelled all holidays up to and including 3 October. It is updating any customers due to travel from 4-15 October.

Jet2 is suspending sale of the country and cancelling all package holidays up to and including 17 October, with all affected customers able to get a full refund or receive £100 off if they rebook. Flight-only customers can rebook without a fee.

Independent tour operator Eco Turkey, which specialises in tailor-made tours, currently has around 70 customers in Turkey, and 200 booked to go between now and January. It had seen a boost for holidays to Turkey over the summer after restrictions were lifted in June, with a relatively busy July, August and September – although numbers are still down around 50% comparedwith last year. However, it has not yet received any bookings for next year, and cancellations are flooding in for the rest of 2020.

“It’s devastating. We’ve already seen cancellations since last night for customers booked from October to January,” said director Ali Keskin. “Other customers who are there now want to come back already, so we are working with chartered flights to get them home.

“We are a small independent tour operator, Turkey specialists, it’s our biggest market. But it’s out of our hands. Most of the countries we sell are on the government quarantine list, so we don’t know where we are going to sell.”

Keskin says that many of the independent hotels it works with face an uncertain future, with some having already closed.

Since Thursday’s announcement, many holidaymakers have struggled to find earlier flights home in order to avoid quarantine, including Amanda Matthews, managing director of travel agency Designer Travel. She told trade publication Travel Weekly that although quarantine exemption is never certain, Turkey looked like the safest option, and was the country she and her colleagues had been suggesting to customers for months. She is currently on holiday with her own family at the Liberty Hotels Lara Beach in Antalya.

“Last night, the news rippled through the whole hotel,” Matthews told the Guardian. “Everyone’s mouths were open in disbelief. Even the staff. You realise these decisions have such a massive impact. Some of the hotels will have to close, people won’t have jobs and won’t have enough money to even live.

“I immediately went online to get earlier flights home, but it was impossible. It’s illogical – there are people here by the pool that are leaving today that won’t have to quarantine, but I’m leaving tomorrow and I will have to. Why can’t you arrive home, self-isolate, order a test online and wait five days for the results, rather than 14 days?”

It’s a sentiment being expressed throughout the travel industry, with many companies calling for airport testing since early May.

“We are nearing the end of the season, and Turkey was an attractive destination for late summer. The sector would have been hoping for a revenue boost for half-term, but that’s getting more difficult now there are very few places left on the list,” said Paul Charles who is calling for a testing roadmap to help boost consumer confidence for 2021.

“This is why we need a testing alternative,” he added. “If the government completely shuts off travel, it won’t help the industry or economy recover. The longer it takes to have a roadmap for testing the more damage we will see to travel in 2021”