Scientific experts have warned of a second wave of the coronavirus pandemic and another complete nation-wide lockdown in the UK unless stricter measures are adhered to amid a rising number of infections in the country over the past week.

Peter Openshaw, a professor of experimental medicine and an expert respiratory medicine at Imperial College London, said the new “rule of six” restrictions on large gatherings which comes in force from Monday is extremely crucial.

"I think everyone is in agreement that we really need to act very quickly now in order to prevent this from growing exponentially and that's the main point, is that we must act fast because it is so much harder to get this sort of thing under control if you delay even a few days,” Openshaw told ‘Sky News'.

"But if we don't do this [rule of six] now we are going to be right back in hard lockdown in short order, that's the only way we have at the moment for controlling this but there are other things on the horizon. We need to act quickly," he said.

"This isn't a game. We shouldn't be out trying to party as hard as we can in the run up to Monday's lockdown. We should all be thinking about what we can do to slow down the spread," he added.

Sir John Bell, Oxford University's Regius Professor of Medicine and member of the UK's Vaccine Taskforce, welcomed the resumption of the Oxford vaccine trials after a brief pause but warned that a COVID-19 vaccine is unlikely to be ready in time for a second wave.

“We're not going to beat the second wave now,” he told ‘The Daily Telegraph'.

“We're probably right at the front end of the second wave now, but a vaccine might arrive towards the end of the second wave… We're probably about three to four months ahead of anybody else with a practical vaccine,” he said.

From Monday, gatherings of more than six people in England will be subject to a 100 pounds fine, rising up to 3,200 pounds for repeat offences. The move was announced by Prime Minister Boris Johnson last this week amid a spike in the number of coronavirus cases across the country.

Meanwhile, police forces shut down a series of illegal parties overnight on Saturday as people tried to make the most of a final weekend before tougher coronavirus restrictions from Monday.

Greater Manchester Police said it had halted illegal gatherings across the city and fixed penalty notices were issued at each of the incidents, which breached existing bans on groups of more than 30 meeting.

Nottinghamshire Police said it issued a “reckless” teenager with a 10,000 pounds fine for hosting a house party which saw more than 50 guests gather in breach of existing rules.

As a result of other localised lockdown measures, nearly 8 million people will be subjected to even tougher isolation measures in the West Midlands and Scotland.

From Tuesday, households in Birmingham, Sandwell and Solihull will be banned from mixing after the region reported a surge in coronavirus cases.

In Scotland, Lanarkshire joins areas around Glasgow subject to tougher controls, with the new rules already in force.

UK government figures revealed the number of new infections were 36 per cent higher compared to last weekend. The rate of the coronavirus recorded through tests conducted largely across care homes on vulnerable age groups had quadrupled since the start of the month and now stands at an estimated 1,100 new cases every day.

“This winter will place unique pressures on the health and care system. COVID-19 will be circulating with seasonal flu and other viruses and transmission may increase,” UK Health Secretary Matt Hancock said in a warning memo to care homes in the country.

The latest warnings come as the dreaded R number, or the rate at which an infection spreads within the community, reached 1.7 – meaning that cases are nearly doubling each week.