The government has announced a £75m airlift operation to rescue hundreds of thousands of British nationals stranded abroad because of the coronavirus pandemic.

The foreign secretary, Dominic Raab, announced a mixture of charter flights to “priority countries” and affordable seats on commercial airlines from countries where they are still running.

After mounting criticism of the Foreign Office approach, Raab announced the government had reached an agreement with British Airways, Virgin, easyJet, Jet2 and Titan to help with the “unprecedented” operation to repatriate people in countries where commercial airlines were no longer flying.

“Under the arrangements we are putting in place, we will target flights from a range of priority countries starting this week,” he said at the daily Downing Street press briefing.

He told travellers not to wait and to book their tickets now even if it meant changing carrier, suggesting the government would subsidise flights.

“Where commercial routes remain an option, airlines will be responsible for getting passengers home. That means offering alternative flights at little to no cost where routes have been cancelled,” he said.

“That means allowing passengers to change tickets including between carriers. So for those still in those countries where commercial flights are still available, don’t wait, don’t run the risk of getting stranded. The airlines are standing by to help you. Please book your tickets as soon as possible.

“Where commercial flights are no longer running the government will provide financial support for special charter flights to bring UK nationals back at home.”

The rescue operation will come as a major comfort to stranded Britons and their families who were despairing about loved ones, including some with medical needs. It is understood the airlift is expected to entail hundreds of flights.

“I was massively relieved to hear that at last our government have listened to the concerns of the thousands of people and their families stranded abroad. It’s been a very worrying week thinking that we may never see our loved ones again,” said Jacqui Phipps from Suffolk, whose daughter is stranded in India.

The shadow foreign secretary, Emily Thornberry, who has been gathering data about stranded Britons, said the £75m sounded good but was just more “vague promises” when scrutinised. “We were promised a new strategy on repatriations today, but for the hundreds of thousands of Brits stranded abroad and their families back home – it was just more of the same.

“More reliance on commercial flights, which – for too many British travellers based in too many locations – are simply not an option at present. More vague promises about charter flights‎, but none of the commitment or urgency other countries like Germany have put into this.

“More expressions of support for our Brits abroad, but no answers to any of the specific problems they are raising, from the loss of travel insurance and accommodation to dwindling supplies of medicine and money,” she said.

The announcement will also infuriate Britons who have already spent thousands to get home after their return flights were cancelled forcing them to switch flights or carriers.

The Foreign Office said it would prioritise the charter flights according to the numbers of Britons stranded and “their vulnerability, including an assessment of the local health provision”, suggesting the risk to those in poorer countries will be deemed higher.

It is thought there are at least 9,000 Britons stranded in New Zealand, 4,000 in Bali, and tens of thousands more in other countries including India, Pakistan and Australia.

Raab said the scale of the operation was “unprecedented” with many struggling to get home causing anxiety to them and their families. Charter flights to Ghana and Tunisia were already under way with two more from Peru due to leave Lima on Monday.

“We’ve not faced challenges like this in getting people home from abroad on this scale in recent memory,” said Raab.

Earlier on Monday, the government conceded it would not be able to repatriate Britons stranded in New Zealand for some time after a telephone call between Raab and the country’s foreign minister, Winston Peters.

The British high commissioner, Laura Clarke, said there would be no “immediate fixes” because the country’s lockdown and the closure of international flights made it near impossible.

“The New Zealand government’s level-four Covid guidance is now absolutely clear in limiting domestic flights and transport to essential works only. That means if you are not close to your departure airport you are going to struggle to get on an international flight home,” she said in a video statement.

UK in New Zealand (@UKinNZ) British Nationals in New Zealand - see below to hear the latest update on the New Zealand COVID-19 situation from British High Commissioner @LauraClarkeUK ⤵️ pic.twitter.com/H9Ff3bqKTN

﻿“I should be clear though that there aren’t going to be immediate fixes to that. It will take at least until the end of March and possibly longer,” she said.

UK in Indonesia (@UKinIndonesia) Our German friends are at it again 🇩🇪👏🏻✈️🏡



They’ve opened 40 places on a flight for 🇪🇺&🇬🇧 citizens leaving Jakarta on Friday 3 April at 17.25, arriving in Frankfurt on Sat 4 April at 05.35.



Cost = regular economy ticket Contact us if you are 🇬🇧 & want to be on that plane ✈️

Germany, which has been leading the way on charter flights, offered 40 seat to British nationals in Indonesia on Monday.

British nationals have been told they can get updates from local embassies and high commissions with a dedicated travel management operation for the charter flights to open imminently.

• This article was amended on 31 March 2020 because an earlier version omitted “shadow” when referring to Emily Thornberry’s position of shadow foreign secretary. This has been corrected.