British Prime Minister Boris Johnson is set Monday to announce an end to all pandemic legal curbs in England, insisting it is time to move on despite political opposition and unease from the UN's health agency.

Two years after Covid-19 sparked the worst health crisis in generations, Johnson will address parliament to outline his plan, pressing ahead despite news on Sunday that Queen Elizabeth II had tested positive for the first time.

However, he stands accused by opposition parties of seeking to distract public attention, with his premiership in peril as police investigate a series of lockdown-breaching parties in Downing Street.

"Today (Monday) will mark a moment of pride after one of the most difficult periods in our country's history as we begin to learn to live with Covid," Johnson said in a Downing Street statement.

"The pandemic is not over, but thanks to the incredible vaccine rollout we are now one step closer towards a return to normality and finally giving people back their freedoms while continuing to protect ourselves and others."

Under the "living with Covid" plan, the government says it intends this week to end a legal requirement for people to self-isolate when infected with the coronavirus.

It says local authorities will be required to manage further outbreaks with pre-existing legal powers, and is expected to phase out free Covid testing for the general public.

The NHS Confederation, which represents senior managers in the state-run National Health Service, said internal polling showed a large majority of its members were opposed to ending self-isolation and free tests.

Matthew Taylor, the confederation's chief executive, acknowledged that the government's mass vaccination programme and the emergence of new Covid treatments offered "real hope".

"But the government cannot wave a magic wand and pretend the threat has disappeared entirely," he said.

'Very unwise indeed'

David Nabarro, a World Health Organization special envoy for Covid, said that scrapping the law on self-isolation was "really very unwise indeed".

While the UK has suffered one of the world's worst per-capita death tolls in the pandemic, it remains a country with "an enviable record for public health expertise", the British official told BBC radio on Saturday.

"I really do worry that Britain is taking a line that is against the public health consensus -- that other countries, other leaders will say if Britain is doing it, why can't we, and this will create a bit of a domino effect around the world," Nabarro added.

In the UK's devolved system, Scotland, Wales and Northern Ireland set their own health policies and are largely staying more cautious than Johnson's intentions for England.

The opposition Labour party said that ending free testing was akin to substituting "your best defender" with 10 minutes to go of a football match.

"Boris Johnson is declaring victory before the war is over, in an attempt to distract from the police knocking at his door," Labour's health spokesman Wes Streeting said.

Downing Street confirmed on Friday that Johnson had submitted a written response to police questions about parties held over the past two years, as detectives probe whether attendees violated strict social distancing and virus prevention rules in place at the time.

He stonewalled questions about the "partygate" affair in a weekend BBC interview, and declined to say if he would resign if he is fined by the police.

But Johnson insisted that despite the apparent party breaches by himself and his staff, the public would still follow guidance to self-isolate when necessary, even without a legal mandate.

"Look at the evidence, look at what the British people have done," he said, referring to general compliance with the rules since the pandemic struck early in 2020.