The Metropolitan Police has responded to more than 1,000 unlicensed events since the end of June, getting information on more than 200 events across the city in a single weekend.
Last week two teenagers were stabbed at a warehouse rave in Borehamwood, Hertfordshire.
In Manchester a 27-year-old woman, said to be the organiser of large illegal gatherings over two consecutive evenings was fined £100 and given an anti-social behaviour banning order preventing anyone outside the household from entering the property.
The new offence will apply to gatherings of over 30 people which are in private dwellings, on boats, or in public outdoor spaces.
