Fines of £800 for people caught at house parties have become law as of 5pm on Friday.
The latest coronavirus laws come into force as part of tougher measures to crack down on illegal gatherings during the pandemic.
The penalty will apply for groups of more than 15 people and will double after each offence, up to a maximum of £6,400 for repeat offenders, Home Secretary Priti Patel said last week when she announced the plans.
This supersedes current fines of £200.
But the £10,000 penalties for unlawful groups of more than 30 people will still only apply to the organiser.
According to the legislation, which has now been published and is called the Health Protection (Coronavirus, Restrictions) (All Tiers and Self-Isolation) (England) (Amendment) Regulations 2021, the £800 fine is cut to £400 if paid within 14 days.
As well as those in private dwellings, the rule also applies to similar gatherings in “educational accommodation”, the documents setting out the new law said.
The new laws give police powers to access Test and Trace data, the documents also suggest.
Human rights barrister Adam Wagner, who studies coronavirus rules and tries to simplify them for the public, said the changes to the law will make it “easier for police to enforce people breaking self-isolation rules”.
Data published by the National Police Chiefs’ Council (NPCC) on Thursday showed 332 fines had been issued by forces in England and three in Wales, to people failing to self-isolate after arriving from a country on the Government quarantine list between September 28 – when the rule came into force – and January 17.
The latest laws, signed off by Health Secretary Matt Hancock on Thursday, amend self-isolation regulations “to correct a number of errors” in previous versions of the legislation and “update the information which may be shared for the purposes of carrying out functions under the regulations, or preventing danger to the health of the public from the spread of coronavirus, and to allow certain information to be shared only where necessary for specified law enforcement purposes”.
The broad definition of who the information can be shared with means it could be provided to police or anyone else the Government may enlist to uphold the rules, such as public health officials.
Contact details, including a phone number and email address where available, can be shared if someone tests positive for coronavirus or if a person has come into close contact with a positive case, the laws state.
Mr Wagner said on Twitter: “Obviously this raises important human rights questions because police will be given access to information about our movements and social interactions. They are only permitted to use that data for the purposes of Covid rules enforcement – but will they?”
He raised questions about whether the data would be kept safe and secure, whether people would be happy with police having access to such data and if enforcement will improve the situation or make people “less willing to share information”.
The Home Office declined to comment and referred the matter to the Department for Health And Social Care – which is yet to respond to questions about the implications of the latest regulations.