It comes as a minister told Sky News that "around a million people" are currently isolating as a result of COVID-19.

Health minister has more details on which workers need daily testing - as PM to face questions over handling of pandemic | COVID latest

"We don't actually collect that data on a daily basis, but it's obvious if you look at how many people tested positive yesterday, about 215,000, that they'll all be self-isolating and obviously from the previous days," health minister Gillian Keegan said.

"So it's about a million people probably are self-isolating right now."

Record numbers of daily cases have been reported recently, as the more transmissible Omicron variant of the COVID-19 continues to spread.

Lateral flow tests 'highly effective'

People experiencing the three official COVID symptoms - a high temperature, new, continuous cough and a loss or change to your sense of smell or taste - would still be expected to get a PCR.

But Sky News understands that those who test positive on lateral flow devices but do not have these symptoms will be told they do not need to take follow-up PCR tests.

It has been reported that health officials have drawn up plans to limit PCR tests to those with symptoms, allowing those who are asymptomatic - about 40% of cases - to return to work more quickly.

People who test positive on lateral flows will still need to isolate for at least seven days, and Ms Keegan told Sky News people will need to register their positive lateral flow results.

At the moment, people without symptoms who test positive on a lateral flow are asked to order a PCR test and to only begin their isolation period when they get the second result.

This effectively requires them to isolate for longer than seven days, especially if there are delays in getting the PCR result.

It is understood the move will be announced on Wednesday.

A UK Health Security Agency spokesperson told Sky News: "We keep everything under review and any announcement will be made in the normal way."

Government sources said lateral flow tests are "highly effective" and testing capacity needs to be prioritised.

Key workers across several industries that keep the country running will be required to take daily lateral flow tests, Boris Johnson announced on Tuesday.

The prime minister said 100,000 workers in England, "from food processing to transport to Border Force", will have to test every day they are working from 10 January.

Meanwhile, ministers are also expected to announce that pre-departure testing will no longer be required for travellers returning to the UK.

PM to face scrutiny as MPs head back to Westminster

MPs will return from their Christmas break on Wednesday, with Mr Johnson holding a cabinet meeting before that.

The PM will face scrutiny over his decision to so far hold off on imposing further COVID restrictions beyond the Plan B measures brought in before the festive period.

He will clash with Labour deputy leader Angela Rayner at PMQs, in a session that is set to be dominated by coronavirus once again.

Labour leader Sir Keir Starmer is isolating after testing positive for COVID for a second time.