And the cost of policing such activities could be more than £250,000, the region’s Deputy Police and Crime Commissioner (PCC) said.
He warned that police were ready to use new powers allowing them to fine organisers up to £10,000.
Authorities in Birmingham were granted a host of new powers on Friday, as a response to the growing number of coronavirus cases in the city.
These include the ability to shut down pubs and other businesses flouting coronavirus rules, while they are also now able to issue fines to the organisers of illegal gatherings.
Speaking during a West Midlands Combined Authority (WMCA) coronavirus update on Friday, deputy PCC Waheed Saleem revealed that nearly 100 gatherings were broken up last weekend – despite Birmingham being placed onto the national watchlist.
It included one event at Babbs Mill park in Solihull, where more than 100 people gathered at an illegal rave.
While over this Bank Holiday weekend, West Midlands Police said it had dealt with around 90 reports from the public about possible breaches of restrictions by Sunday morning – but added "we have not had to use our enforcement powers".
The force said the weekend had so far "been dominated by reports of house parties, rather than the really big gatherings we have seen earlier in recent weeks".
On Saturday, officers swooped on a large gathering at an unnamed Black Country pub – after a resident said their 'windows were shaking' from the music.
West Midlands Police revealed they were called after an alert of more than 100 people partying – but after speaking to the organiser who had a coronavirus risk assessment in place allowing for more than 100 people outside. Officers said the event could continue as fewer than 80 were in attendance.
Speaking at the WMCA update, Mr Saleem said: “Last weekend [August 22 and 23] we broke up 96 gatherings including one where 100 people were gathering at the Babbs Mill park in Solihull having an illegal rave.
“These events are not only breeding grounds for the virus and for people to spread the virus beyond to their loved ones, but they’re also a breeding ground for criminality as well.
“I expect that this special operation is going to cost us over £250,000 over the summer months in overtime and extra resources.
“I’d rather we spent this £250,000 on dealing with other pressing issues, and our demand rates have gone up to pre-Covid levels, but unfortunately we are utilising these resources to try and close down these illegal gatherings.
“I would urge people not to organise these illegal gatherings – we will issue these significant penalties now these powers have been given to us.
"Of course we will always do the four Es approach of engaging, explaining and encouraging people, but it’s come to a point where we will now look at enforcement as well and utilising these additional powers.”