UK Prime Minister Boris Johnson on Monday tabled a four-step cautious roadmap in Parliament for the country to be eased out of its strict stay-at-home lockdown, with a tentative June 21 timeline for most limits on social contact to be lifted if the coronavirus infection rates remain under check.

In the first phase, schools will be reopened from March 8 and, under a minimum five-week gap between each phase of relaxation, outdoor gatherings will be allowed from April 12 before more indoor settings such as pubs, cinemas and gyms being allowed to reopen by May 17.

Finally, June 21 is expected to mark an end to all lockdown measures but Johnson was keen to reiterate that this roadmap would be data rather than dates driven because the deadly threat from the virus currently "remains substantial".

"(The roadmap) will guide us cautiously but irreversibly towards reclaiming our freedoms," Johnson told members of Parliament in the House of Commons.

"We are able to take these steps because of the resolve of the British people and the extraordinary success of our NHS (National Health Service) in vaccinating more than 17.5 million people across the UK," he said.

Johnson stressed that it was impossible to achieve a "zero-Covid" status because there will always be some vulnerable people who are not protected by the vaccines", even as he acknowledged that the lockdown restrictions cannot remain in place indefinitely because of the impact on the economy and the physical and mental well-being of people.

The unlocking strategy was finalised at a virtual Cabinet meeting earlier on Monday and MPs will now get a vote, following which the final roadmap will kick into action in the coming weeks.

Our decisions will be made on the latest data at every step, and we will be cautious about this approach so that we do not undo the progress we have achieved so far and the sacrifices each and every one of you has made to keep yourself and others safe. We have therefore set four key tests which must be met before we can move through each step of the plan, said Johnson.

The key tests cover four aspects: the vaccine deployment programme continues successfully; evidence shows vaccines are sufficiently effective in reducing hospitalisations and deaths in those vaccinated; infection rates do not risk a surge in hospitalisations, which would put unsustainable pressure on the NHS; and the assessment of the risks is not fundamentally changed by new "variants of concern.

After schools reopen on March 8, some outdoor restrictions will be lifted by March 29. Non-essential retail, hairdressers, nail salons, gyms and outdoor areas in hospitality venues are likely to reopen along with libraries, museums, zoos and theme parks from April 12.

From May 17, the hope is that pubs, restaurants, cinemas, hotels and children's play areas will welcome back people and fans will be allowed back into sporting events.

Most rules on social contact outdoors will be lifted, while mixing of different households will be allowed indoors and up to 30 people will be allowed at weddings, funerals, wakes, receptions and christenings.

And by June 21, the government expects all legal limits on social contact can be removed, with the remaining sectors of the economy reopened.

Before proceeding to each next step, the government said it will examine the data to assess the impact of previous easements. Due to the current relatively uniform spread of the virus across the country, restrictions will be eased step-by-step across the whole of England at the same time.

Downing Street said that the four tests are currently being met so the first step will proceed from March 8, at which point the top four priority cohorts for vaccinations as determined by the independent Joint Committee on Vaccination and Immunisation (JCVI) will have received a degree of immunity, three weeks after being offered their first dose.

The roadmap is described as a means to balance social and economic impacts, whilst preserving health and safety. Outdoor settings are known to be lower risk than indoor in keeping infection rates low, so outdoor activities will be opened earlier than indoor ones.

The devolved administrations of Scotland, Wales and Northern Ireland have been setting out their own roadmaps for easing lockdown, but are in most part following a similar phased approach.

As part of the new roadmap, the Public Health England (PHE) will publish new data on the impact of vaccines on transmission rates. Early data suggests a reduction in transmission of the virus in people who have had a vaccine.

So far, more than 17.5 million people in the UK have received a vaccine dose and over the weekend the government set a new July 31 target to ensure all adults have received their jabs to protect against the deadly virus.

PTI