Travellers arriving in the UK under the new quarantine rules will be allowed to leave isolation in order to shop for food and other essential supplies.
Boris Johnson announced in May that all arrivals in Britain will be forced to quarantine for a fortnight in a bid to fight the coronavirus pandemic.
But the quarantine order has been met with criticism by businesses and has led to unease in the Tory ranks with concerns the quarantine will be "unenforceable".
The new rules are expected to be set out by Home Secretary Priti Patel on Wednesday.
The restrictions, which are due to come into force on June 8, will be similar to those imposed during the coronavirus lockdown.
Mr Johnson's official spokesman said: “I think there will be a limited set of exemptions, just as there was during the nationwide lockdown.
“For example, I would expect people only to be able to leave the property in which they are quarantining if they need urgent medical treatment, support from social services, food or medicine which they cannot get delivered or get anybody else to bring to them, an emergency in the place they are staying – such as a fire – or to attend a funeral of a close relative.”
Travellers will also be able to board public transport from the port or airport to where they will quarantine, although they will be encouraged to use private vehicles instead.
The guidance “suggests that people should take private vehicles wherever possible”, the spokesman said.
The Government is still looking at the prospect of “air bridges” between the UK and other countries which would be exempt from the quarantine rules, with Boris Johnson reported to be in favour of the plan.
The Prime Minister’s official spokesman said: “There is no change on air bridges, we have said it’s something which the Government is looking at.”
But the spokesman added that the policy was focused on stopping “imported cases of this virus” and “one of the most devastating things which could happen to the economy is to have a second spike”.
Former transport minister Stephen Hammond called for the plan to quarantine all people arriving from outside the UK to be scrapped.
The Tory MP told BBC Radio 4’s Today programme that air bridges would be a “sensible, targeted response” between low-risk countries.
“I think the idea of air bridges are the right way forward,” he added.
“I think, as we’ve seen across the world, people are taking measures out of the lockdown and this targeted approach would be a much more sensible way to behave.”
George Morgan-Grenville, CEO of tour operator Red Savannah, said: “By pursuing its quarantine plans without due regard for the economic consequences, the Government is choosing to ignore the devastation it will cause to companies, to employment and to the lives of all those whose jobs will be lost.
“The quarantine measures are a blunt weapon which will bring only economic disaster.”
Professor John Newton, the national testing coordinator, said contact tracing for travellers arriving in the UK could be used instead of quarantine measures.
He told the Downing Street briefing that the 14-day self-isolation for arrivals would not be necessary if the risk of the traveller having coronavirus is sufficiently low, or if a case can be quickly responded to with a test and trace programme.
“If travellers are able to be tested and self-isolate in response to contact tracing – just like a domestic new case – then that would also be a way of dealing with it.”