British holidaymakers who have had both coronavirus jabs could enjoy more quarantine-free travel from August under government plans to rescue summer breaks.

Ministers are set to announce an overhaul of travel restrictions on Thursday. While they are not expected to add a significant number of countries to the green list, they are likely to unveil plans to exempt travellers with two vaccine shots from the requirement to quarantine for ten days after visiting an amber list destination.

Yesterday Matt Hancock, the health secretary, raised hopes that the plan could salvage summer holidays, telling BBC Breakfast: “We’re not ready to be able to take that step yet, but it’s something that I want to see and we will introduce, subject to clinical advice, as soon as it’s reasonable to do so.”

However, Boris Johnson warned that there were still likely to be delays and “hassle” for holidaymakers.

The prime minister said during a visit to Hertfordshire: “I want to stress that this is going to be, whatever happens, a difficult year for travel.

“There will be hassle, there will be delays, I am afraid, because the priority has got to be to keep the country safe and stop the virus coming back in.”

The traffic light system for foreign travel was introduced last month. Travellers returning from countries on the amber list have to isolate at home for ten days and take a PCR test on the second and eighth day.

Government sources downplayed hopes of a mass reopening of international travel this week, insisting that only a “handful” of countries were in contention to be added to the green list.

A Whitehall insider said: “The science says we could add lots of countries to the green list but some ministers are taking a different view.”

The PC Agency, a travel consultancy, said that at least 14 amber countries could be added to the green list because Covid-19 case rates are less than half those in the UK, which has recorded 131.3 infections per 100,000 people over the past two weeks. They include Barbados, Malta, Morocco, Poland, Mexico, the Balearic Islands, Germany, Italy, Croatia and the US.

At the same time as announcing the review of the green list, ministers will confirm plans for double-jabbed Britons to enjoy quarantine-free travel to amber list countries. A senior government source said that July was likely to be too early to implement the scheme but by August enough people will have received both jabs to enable the government to push ahead.

Eighteen-year-olds will start receiving their second dose by mid-August, which ministers believe will justify the introduction of vaccine passports for foreign travel.

A potential obstacle to the plans is how to treat children, who have not yet been approved for the jab. The Times understands this has led to an idea within some parts of government to hold off from the quarantine exemption until September, to avoid an influx of children returning from foreign holidays and spreading the virus in schools. However, any delay in reopening mass foreign travel could harm the economy.

An analysis published today by the World Travel and Tourism Council (WTTC) says the UK would take a £19.8 billion hit if most international travellers are, in effect, barred from entering the UK for the whole of July.

Virginia Messina, senior vicepresident at the WTTC, said: “We simply can’t afford any further delay. We are running out of time, with many businesses facing going bust if international travel doesn’t resume in July.”

Yesterday, airlines also wrote to Grant Shapps, the transport secretary, calling for the existing “disproportionate” border restrictions to be scrapped.

The letter from Airlines UK, which represents carriers such as EasyJet and BA, points to the fact that at least 32 countries already exempt arrivals from quarantine if they are fully vaccinated.

Johnson’s gloomy outlook came despite NHS Test and Trace data revealing that just 0.1 per cent of the 3,124 arrivals in Britain from Spain, France and Greece tested positive for the virus between May 20 and June 9.