Car clampers were blockaded inside a car park for four hours by residents at a block of flats in Southend, Essex.
A new parking scheme was introduced outside the flats in Prittlewell, but clampers immobilised 16 cars before residents had received their permits.
Residents responded by using their vehicles to blockade the clampers, then refused to move during a stand-off.
London Parking Control said it had carried out its duties correctly and in accordance with official guidelines.
The company is now liaising with Essex Police to see if the barricading was in any way illegal.
"We barricaded them in across the arch so the clampers could not get out so there was a stand-off," resident Scott O'Brien said.
Lisa Stiles found her car clamped when she was about to take a five-month-old girl to a hospital appointment.
Ms Stiles confronted the clampers and informed them it was her own private parking bay.
"They just said 'well, if you don't pay the fee you will have to pay to have your car collected when it is removed'."
The fine cost Ms Stiles £125, plus a £5 fee on her credit card.
"I was very upset, it made me cry," she added.