Boris Johnson has said England is approaching “seasons of hope” that will usher in changes making lives “incomparably better” as he set out a plan to ease the lockdown by June 21.

The Prime Minister defended his “cautious but also irreversible” approach to relaxing restrictions with a four-step plan on Monday, arguing he will not be “buccaneering” with people’s lives.

But despite billing his plans as a “one way road to freedom”, he admitted he could not guarantee that restrictions will not have to return, as he aims for the impact of the vaccination programme replacing the need for lockdown measures.

He accepted that scientific modelling suggested that lifting measures will increase Covid-19 cases and ultimately deaths, but insisted the restrictions could not continue indefinitely.

And he acknowledged that there are ethical issues around vaccine certificates, after launching a review to determine whether they could be used by venues or firms.

In the first step of the road map, all pupils in England’s schools are expected to return to class from March 8, with wider use of face masks and testing in secondaries.

Socialising in parks and public spaces with one other person will also be permitted from that date.

A further easing of restrictions will take place on March 29 when the school Easter holidays begin with larger groups of up to six people or two households allowed to gather in parks and gardens.

But progressing along the “road map” will depend on meeting four tests: the success of the vaccine rollout, evidence of vaccine efficacy, an assessment of new variants, and keeping infection rates below a level that could put unsustainable pressure on the NHS.

The other points when restrictions may be eased at the earliest are:

– April 12, when shops, hairdressers, nail salons, libraries, outdoor attractions and outdoor hospitality venues such as beer gardens may reopen.

– May 17, when two households or groups of up to six people may be allowed to mix indoors and crowds of up to 10,000 in the largest venues will be allowed at performances and sporting events.

– “As soon as possible” and no later than step three, when ministers committed to reviewing social-distancing guidance that has prevented loved ones from hugging for nearly a year.

– June 21, when all remaining restrictions on social contact could be lifted, larger events can go ahead and nightclubs could finally reopen.

Mr Johnson told a Downing Street press conference: “Thanks to the vaccinations there is light ahead, leading us to a spring and a summer, which I think will be seasons of hope, looking and feeling incomparably better for us all.”

But with some Conservative lockdown-sceptics arguing that the plans are too cautious, Mr Johnson denied he was being a “gloomster”.

And he said he will not “be buccaneering… with people’s lives”, after figures showed there have been 140,000 deaths involving Covid-19 in the UK.

But with the threats that new variants present, he acknowledged: “I can’t guarantee it’s going to be irreversible, but the intention is that it should be irreversible.”

Chief medical officer Professor Chris Whitty urged the public to stick to the rules as lockdown is eased, warning of a “very rapid surge in infection” if they relax too early.

He said there are still “very significant” numbers of people with coronavirus every day and many people still in hospital with the disease, but said now is the point for a “steady, risk-based, data-driven opening up”.

Professor Whitty added that coronavirus was “likely to be a problem” during the winter months “for the next few winters”.

The Government launched a review looking at the use of “Covid status” certificates, which could be used by people to demonstrate they had received a jab or a negative coronavirus test in order to enter venues, or allow firms to reduce restrictions as a result of the status of their customers.

Mr Johnson said there are “clearly some quite complex issues, some ethical issues” including discrimination surrounding them, but added: “There may well be a role for certification but we just need to get it right.”

International travel rules will also be reviewed, with May 17 targeted as the earliest possible date for a foreign holiday.

A further piece of work to conclude by June 21 will examine social-distancing requirements, the use of face masks and requirements to work from home.

A series of pilot events will also be held from April using enhanced testing and other measures to examine how larger crowds could be allowed to attend sporting events or performances.

The Prime Minister earlier told MPs his approach would be driven by “data not dates”, with the five-week gap between stages allowing time for the impact on infections to be determined and for companies to get ready.

The road map will be put to a Commons vote before the House rises for Easter in late March.

With the plans depending on the success of the vaccine programme, Mr Johnson hailed data from Public Health England that showed a single shot of the Pfizer jab cuts the chance of hospital admission and death from Covid-19 by more than 75% among the over-80s.

He also indicated that the continued restrictions on some businesses will lead to an extension in taxpayer-funded support schemes, saying: “We will not pull the rug out.”

Chancellor Rishi Sunak is under pressure to extend measures such as the furlough scheme, which is due to expire at the end of April, when he delivers his Budget on March 3.

Conservative MP Steve Baker, the deputy chair of the Covid Recovery Group of Tory lockdown-sceptics, said the “pace of change will be a hammer blow” to industries such as aviation, hospitality and the arts.

While all pupils will return to England’s schools on March 8, in Scotland and Wales the phased return of children to classes began on Monday.

Scotland’s First Minister Nicola Sturgeon will set out her plan to exit lockdown on Tuesday, while Welsh counterpart Mark Drakeford has suggested stay-at-home orders could be eased in around three weeks.

In Northern Ireland, First Minister Arlene Foster has promised a “decision-making framework” on how the executive plans to exit lockdown will be published on March 1.