Two police officers were injured as they attempted to shut down an illegal rave in Milton Keynes over the weekend.
A “large, hostile crowd” turned violent as officers tried to end the rave in Petsoe Manor Farm, Emberton.
There have already been seven people arrested in connection with the illegal gathering on Saturday.
Mark Lancaster, MP for Milton Keynes North, described the events as “deeply concerning”.
He said: “The level of violence on Saturday is something we have simply never seen before.
“It’s horrifying and unacceptable.”
A police helicopter, mounted section and police dogs were all used during the rave, but it was not fully shut down until Sunday afternoon.
Councillor Peter Geary, who represents Olney, says the police were hailed with “bottles, bricks and stones” during the violence.
He said: “It caused a lot of disturbance and damage. It is a really concerning event.
“At this time of year it is fairly easy for people to gain access and cause a mess, but there will be lessons learnt - the most important thing is that is was closed down.
“It’s difficult because if the police had stood back and not done anything, we would have criticised them, but they did go in there and two officers were attacked.
“I think they made a good decision to go in despite the hail of bottles, bricks and stones they got when they came under assault.
“They were very brave and should be praised for the way they handled the situation.”
Seven people were arrested on suspicion of organising an illegal rave, public order offences and criminal damage.
Supt Ed McLean says a robust criminal investigation will follow the weekend’s events.
He said: “I would like to thank the local community once again for its patience throughout this incident.
“Attempts had been made earlier to put a halt to this illegal rave, but unfortunately officers were prevented from doing so by a large hostile crowd.
“I would like to thank Supt Christian Bunt for commanding this incident and officers at the scene, who have shown real courage and patience.
“Thames Valley Police will not tolerate such illegal activity and a robust criminal investigation will follow.
“Our officers have remained at the scene to ensure people have left the area in a peaceful manner and to offer reassurance.
“Local Neighbourhood Officers will be visiting landowners and residents in the coming days to address any concerns they may have.”