People with coronavirus symptoms look set to have to self-isolate for 10 days - three days longer than the current minimum.
Government insiders say the move is set to be announced in an effort to stop a new spike of infections.
The Chief Medical Officer is due to make an announcement later today after details leaked to a string of newspapers overnight.
The Times and Daily Telegraph report people will need to self-isolate for 10 days after their symptoms begin.
Currently it is 7 days - even though those people's close contacts, their households, and people coming back from Spain, must all isolate for 14 days.
The current difference is between people who could be incubating the virus, and haven't yet got symptoms, have a longer period before they are safe.
However, lengthening the 7-day period would bring the rules closer in line with quarantine regulations for those returning from countries such as Spain.
It comes as increases in new cases spark alarm, with Oldham overtaking Leicester as the second worst coronavirus hotspot in England, behind Blackburn with Darwen.
Asked about the move, Health Secretary Matt Hancock told Sky News: “This is a decision that’s clinically led. The chief medical officer will be setting out details later today.
“I can’t steal his thunder but what I will say is we will always do what is necessary to protect people and we’re guided by the clinical judgment, by the science in this.”
Mr Hancock warned that a “second wave” of coronavirus is “starting to roll across Europe”.
He added: "There is a serious concern about a second wave that's clearly now moving across Europe and we need to take action - action to protect this country and protect everybody in it.
"And if that means increasing the number of days that people who tested positive have to self-isolate then so be it because these measures are necessary to keep people safe."
Ministers are also looking at a second possible change to isolation rules - which is not expected to be announced imminently.
That second idea is to reduce the two-week quarantine period in which people must isolate when coming to the UK from overseas.
Mr Hancock confirmed the idea is being looked at and would revolve around testing people to ensure they're safe.
He added: “We have asked the scientists to do that work and they’re doing that work, but we’re not ready to change that policy.
“We won’t be making changes on that in the next few days.”
Boris Johnson is worried about a second spike of the virus, with the official death toll now standing at 45,961.
But the true figure is likely to be far higher.
Last week the Office for National Statistics (ONS) said a decline in new cases "has now levelled off".
In the week up to July 19, around one in 2,000 people were estimated to have coronavirus in the community in England.
But the previous week's bulletin put the figure one in 2,300.
There were an estimated 2,800 new cases per day, compared with 1,700 the previous week.
So far the ONS has not said there is a statistically significant rise - but new figures will be published tomorrow.
Mr Hancock refused to say if the figures will show an exponential increase.
Niall Dickson, chief executive of the NHS Confederation, said that the combination of a spike of cases with "exhausted staff" while the NHS tries to rebuild services could prove "challenging".
He told the All-Party Parliamentary Group (APPG) on Coronavirus: "I would say in relation to the second spike issue or something coming, the levels of concern among our members - the people who are leading NHS trusts, who are leading in primary care and all levels in the systems - is very high.
"There's real concern about winter and the compounding factors there, but also about an earlier spike."
He said non-Covid-19 productivity in NHS trusts was currently at about 60%.
Meanwhile, he called for an "Amazon-style" way for the health and care system to order personal protective equipment (PPE) - whereby they can order it and have it arrive the next day.
New data shows there are 54.3 cases per 100,000 people in Oldham - slightly higher than Leicester's 53.2.
Blackburn with Darwen, in Lancashire, remains the worst-affected area, with 85.9 cases per 100,000 people.
Manchester, Trafford, Bradford and Rochdale are also among the places where the infection rate is high, data from Public Health England shows.
An estimated 235,000 residents in Oldham have been told not to allow visitors into their homes, and stay two metres apart while outdoors.
