The public is being warned not to bow to peer pressure to break Covid rules as the first major easing of lockdown restrictions takes effect.
From Monday, people can meet outdoors in groups of six or two households in private gardens, parks and beaches as temperatures soar.
As well as allowing barbeques, picnics and group walks, the relaxation of "Stay Home" restrictions will see the return of organised sports such as football and cricket and the opening of outdoor swimming pools, tennis courts and golf courses.
But a new Government advertising campaign will urge people to "take the next steps safely", telling them not to give in to pressure to hug, sit closer than two metres apart from others outdoors or to meet indoors.
The guidance "reiterates the importance of sticking to the rules, resisting the temptation to hug people who aren't in the same household or bubble", officials said.
The public will be told that "it's OK to say no" to anyone putting them under pressure to meet in larger groups or break the rules in other ways.
With a heatwave expected this week and some schools having already broken up for Easter, there is concern within the Government that some could abandon the rules, with fears of large gatherings and parties as crowds flock to popular areas.
There are also fears that people could be tempted to shift outdoor activities indoors as the weather cools towards the Easter weekend. Reflecting the concerns, the Metropolitan Police said on Sunday that it would be sending more officers to public spaces, with Scotland Yard saying it made "no apology for our tough stance on shutting down large gatherings".
The message of caution from the Government comes despite the success of the vaccine rollout, with more than 30 million people in Britain having now had a jab – around 57 per cent of all adults. The number of new daily Covid cases dropped to 3,768, the lowest since mid-September.
However, Matt Hancock, the Health Secretary, said: "Every day we get closer to beating this virus. We have already vaccinated over half of the adult population and we have new vaccines coming on stream, but we must remain vigilant.
"I know the last few months have been challenging, and many people are excited to be able see friends and family outdoors for the first time in months.
"But as we see from rising cases in Europe, this virus still poses a very real threat. We have come so far thanks to the vaccine rollout, and that progress must be protected. So let's take this next step safely when you meet others do so outdoors, and keep a safe distance."
The Tory MP Steve Baker, who chairs the Covid Recovery Group, said the latest restrictions remained "draconian", accusing ministers of creating a "dystopian society".
Writing for The Telegraph, he said the Government could "begin to cash in on the stellar success of the vaccine rollout by treating us as responsible adults" who could decide for themselves whether physical contact was too risky.
"People who think a tempting hug might still be high-risk can refrain, while low-risk people should be free to choose normal interaction," he wrote, saying the public should be allowed to take responsibility instead of being "bossed about under a shifting blanket of minute rules".
However, ministers also expressed pessimism over the weekend about this being the last lockdown, with Oliver Dowden, the Culture Secretary, saying that "you can't rule things out" and saying he could not guarantee that all legal restrictions on social distancing will end in June.
Mr Dowden hailed the importance of the return of grassroots sport and its importance for "our nation's physical and mental health".
Mr Johnson echoed his comments, saying he hoped a "great British summer of sport" was on the way and writing on Twitter: "Ahead of outdoor organised sport returning across England, good luck to everyone getting back to the sports you love – from football to netball and much more."
Boris Johnson also stressed the need for caution, saying: "I know many will welcome the increased social contact, with groups of six or two households now also able to meet outdoors.
"But we must remain cautious, with cases rising across Europe and new variants threatening our vaccine rollout. Despite these easements, everyone must continue to stick to the rules, remember Hands, Face, Space, and come forward for a vaccine when called."
In the new Government advice, the public will be urged not to be tempted to meet indoors because the risk of spreading Covid is significantly higher inside.
"Saying 'No' has never been more important, so try not to fall victim to peer pressure," the advice, written by psychologist Laverne Antrobus, says. "Be clear that you are following the rules and that meeting up in a group of six and staying outside is the safest way to be with each other at the moment.
"Be firm if people suggest breaking the rules. You may find yourself having to be quite firm if others suggest breaking the rules, e.g. to have a hug.
"When out in public, sitting apart might feel strange and it may be tempting to sit or stand closer to others, but the two-metre distance is still really important."
A new advertising campaign will also urge people to open windows to improve ventilation in their homes, and presents the Government's new "Hands, Face, Space and Fresh Air" slogan.
Health officials said it was important that those who have had a vaccination continue to follow the rules as the full impact of jabs on transmission is not yet known.