Humberside has become the first police force to create a dedicated online "portal" where people can submit written tip-offs if they spot gatherings of more than two people.
Other forces including West Midlands, Greater Manchester and Avon and Somerset are urging the public to alert them to breaches using their established online forums rather than 999 or 101.
It has already seen one late-night house party in Coventry broken up by police and eight people "removed" and sent home after a neighbour tipped off West Midlands Police.
Police chiefs, however, also urged snoopers to apply common sense after receiving calls from people demanding officers come and arrest a neighbour for "going on a second run" in a day and another calling for urgent action against a neighbour apparently driving off for the day.
On Friday Martin Hewitt, chair of the National Police Chiefs' Council (NPCC), said the police action was being taken because "this is a national emergency, it is not a national holiday."
He said officers would adopt a proportionate approach to public tip-offs but welcomed them as a "positive" sign that people were "letting us know" and taking the crisis "seriously."
The NPCC confirmed people had already been fined within the first 24 hours of the new regulations including it is thought a woman taken for a drive with a friend and another spotted in her car by the same police officer on three separate occasions.
The moves on snoopers however, provoked further criticism from civil liberty campaigners following Thursday's deployment of drones to track walkers in the Peak district and road checks in North Yorkshire, Devon and Cornwall.
Silkie Carlo, of Big Brother Watch, warned it was an "ill-advised" use of resources at a critical time. She said: "We don't want to become a nation of informants. Citizen policing is characteristic of authoritarian regimes and doesn't reflect the community spirit most Brits are tackling this crisis."
The Bruges Group warned: "This is not East Germany. We do not want Britain to sleepwalk into becoming a Police State in which we fear our neighbours."
Humberside said it introduced the web portal because of a surge in 101 calls about breaches but urged people to exercise discretion over tip-offs.
"For instance, if a couple and two children are seen in the park, it's highly likely they are all from the same household and are taking the opportunity for their one form of exercise of the day, which under the guidance is allowed," said the force.
"However, if there is a group of ten people of the same age gathered in a car park, it's more likely they are not from the same household. We will not be able to deploy officers to every single report of social gatherings...the information within the report will determine our response."
Nick Adderley, Northamptonshire's chief constable, said the force had been inundated with dozens of 101 calls about breaches and was prioritising tip-offs about gatherings of "five, six or seven or more."
However, he said the force's intelligence unit assessed all information for "patterns of behaviour" or a "consistency" in the way people acted that might merit further investigation.
Besides calls about neighbours going on second runs, the force has received reports of neighbours gathering in their back gardens and he pledged the police response would be "proportionate."
"We won't have police officers crashing through garden fences to check the ID of everyone who is there to see whether they live at the house or whether they should be self-isolating," he added.
Yesterday also saw Britain's first "coronavirus injunction" imposed by a Manchester housing association on an unruly tenant who was throwing noisy parties with 20 guests during the lockdown.
Mosscare St Vincent's association went to court to get the legal order preventing further disruption after receiving complaints from worried neighbours about the parties.
Meanwhile, South Wales Police has teamed up with Neath council to use drones with megaphones to search "hotspot" areas where people are defying the rules and broadcast advice, while Haringey council urged people to report construction workers breaching social distancing rules to the police.
Mr Hewitt denied the police was becoming an "arm of the state," though it was working "extremely closely" with the Government.
He said forces aimed to strike a balance between taking action to prevent the spread of coronavirus and not "damaging" the relationships between police and public.
He confirmed the military could be brought in to bolster police numbers with up to a fifth of officers expected to be off sick or self-isolating in the Government's worst-case coronavirus scenario. They would most likely take up back office roles freeing up officers for the frontline.
To plug the gaps, Dame Cressida Dick, the Metropolitan Police commissioner, is writing to all officers who retired in the last five years to ask them to re-join the force or come back as special constables.
It follows Government changes to tax and pension rules to remove financial disincentives.
She is also asking Met officers nearing 30 years' pensionable service, to delay their retirement and stay on.
Groups are completely INCAPABLE of applying common sense! I trust that's why they put this add on pablum was added - for the sake of appearance, not in hope of any substantive change.