Boris Johnson is set to urge the public to accept “one last heave” to freedom as he delays the final step of lockdown reopening.

On Sunday night the Prime Minister was finalising his plan to push back the June 21 reopening in England by up to four weeks owing to a surge in Covid cases. Earlier in the day he had refused to rule out further delays in the future. 

It means rules ordering the wearing of face masks, limiting groups to six people indoors and 30 outdoors, and keeping nightclubs shut are set to remain in place.

The cap on weddings being attended by only 30 people is expected to be relaxed, but the exact details of what new rules would replace it were still being debated in Government on Sunday night.

Mr Johnson’s message to the nation at a Downing Street press conference on Monday evening is expected to be that sticking to the rules now is worth it to avoid a future lockdown. 

It comes as industry body leaders warned that compliance with the restrictions could slip, with pub staff already facing abuse from drinkers when enforcing the rules.   

A senior UK government source said: “The message has always been cautious but irreversible. That has been our mantra throughout and that continues.

“It would be far worse to have uncertainty and go backwards. It is better to be cautious and have certainty. It is one last heave. It is a straight race between the vaccine and the virus.” 

Tory MPs were vowing to vote against extensions to the laws that enshrine Covid rules on Sunday night, which had been due to expire at the end of the month but will now be renewed.  

Well-placed figures across Whitehall expect Mr Johnson to announce a four-week delay in the final step of reopening, taking the reopening date to July 19, with a review after two weeks.

However, there are fears the delay could ultimately last even longer if the third wave of Covid cases continues to soar.

Covid cases projection – June 21

On Sunday, the Prime Minister did not rule out further future delays when asked by The Telegraph at the end of the G7 summit in Cornwall, raising fears of lockdown stretching into August.

Downing Street’s argument for the extension is that it buys the country more time to both monitor the delta variant – first found in India – and, crucially, deliver millions more doses of the vaccine.

In the last week the Government has delivered around 170,000 first Covid vaccine doses a day. At that rate, some 4.5 million more first doses could be delivered in the four-week delay.

And if they shorten the time that people in their 40s have to wait for their second jab – as Scotland did this weekend – analysis suggests they could deliver as many as 12 million jabs.

Dominic Raab, the Foreign Secretary, stressed the importance of second doses – at which point people get the fullest immunity possible – during an interview on Sunday.

Mr Raab told BBC One’s Andrew Marr programme: “The race we are in is to get everyone as far as we possibly can to two doses”.

Latest UK vaccine numbers: rollout figures

But Mark Harper, the Tory MP who chairs the lockdown-sceptic Covid Recovery Group, cautioned that waiting until everyone was double jabbed would mean not reopening fully until late September.

There were warnings on Sunday that adherence to lockdown rules could become strained if the justification for the reopening delay is not clearly communicated to the public.

Chris Naylor, UK Weddings Taskforce chairperson, predicted that some couples might decide to start holding large weddings if tight limits on attendees remain.

“I think people will start taking things into their own hands. As a sector we have been very much respectful of the rules,” he said.

“But seeing what some people have been saying on social media I think people will start moving away from venues and having weddings in their back gardens and other places.

“It is so stressful for people and businesses. In some cases couples have moved their weddings four or five times. It’s been a real rollercoaster.”

One industry body leader, who asked not to be named, said that sometimes in pubs and restaurants staff were being abused when trying to police the Covid rules.

“People say they don’t want to wear masks or check in for contact tracing. If you don’t see the point of the law there is less respect for it and less willingness to comply,” they warned.

The Telegraph understands that the Government is planning to extend the law that enshrines the Covid rules of the reopening roadmap, which are due to expire this month.

While Mr Johnson would likely have the numbers to win a vote on the law extension in Parliament, since Labour is supportive, it would likely be opposed by vocal Tory backbench critics.

Steve Baker, Conservative MP, said: “Boris Johnson will certainly face a number of rebellions over extending various aspects of these restraints. I’m clear I’m for dismantling this apparatus entirely.”