Anyone who attends a party or other illegal indoor gathering of more than 15 people risks being fined £800 following new legislation introduced from 5pm today.

The new fines – four times larger than those previously available for attendees - will apply to many of the types of illegal gatherings, parties and raves which police have had to break up in recent weeks and where attendees have previously faced £200 fines.

Commander Alex Murray, the Met's lead for Covid-19 enforcement, said: "If you are planning on attending an illegal gathering, party or rave this weekend you are not only taking a very serious health risk but also a much bigger financial risk.

"I hope that these increased fines will discourage some of the events we've seen in recent weeks - events which are no doubt adding to the already huge pressure on our health services and potentially leading to avoidable deaths."

Police will still issue fines for any illegal gathering of two or more people; these start at £200 for a first offence but rise to £10,000 fines for organisers of gatherings of over 30 people. Figures published on Thursday showed that the total number of fines issued by the Met throughout the pandemic increased by nearly 80% in just four weeks during December and January. This followed instructions to officers to move more quickly to enforcement.

Commander Murray added: "We know there are some who continue to ignore the rules. The wider public who have done so much to keep the virus under control want to see us taking the enforcement action we have been.

"Our officers are moving much more quickly to issuing fines because there is simply no excuse for some of the blatant, dangerous and wilful breaches that have been taking place while our city is at such a critical point of this pandemic. That swift enforcement approach will continue.

"If you plan to party this weekend, be warned, it could be very costly - first to your health, but also your pocket."