Motorists were caught on the hop as Perth and Kinross Council implemented new rules at its South Inch car park.
Barriers at the site have previously been raised at 6pm, allowing some drivers who have been parked at the site for several hours to leave without paying.
It is believed that the council has been losing tens of thousands of pounds due to motorists taking advantage of the loophole.
However, the barriers will now remain lowered 24 hours a day, though parking will remain free between 6pm and 8am.
The move sparked chaos, and even resulted in a crash, when it came into force on Friday evening, with several drivers forced to reverse from the barrier after realising it would not rise.
One vehicle collided with the car queueing behind it.
Some motorists were angry that the change was made with little warning. Perth and Kinross Council announced the alteration on their social media channels late on Thursday evening but no signs were placed within the car park itself.
Laura Appr, who travels to work in Perth from Fife, arriving before 8am and leaving after 6pm, said: “I am furious they could have given a bit of warning. I don’t mind paying but I would have liked prior warning so I could have bought a season permit.
“A lady in a car stopped me and said the barriers are now 24 hours that’s the first I knew of it. Announcing it online is just unprofessional.”
Robert Shepherd, from Milnathort, added: “It used to always go up at 6pm and if they are going to change it they need to tell people.
“I’m angry that no one has been told putting it on Facebook is not informing people, there should have been signs in the car park.
“Parking in Perth is a nightmare at the best of times. I’m of the opinion they should have more free parking to encourage people to come to the city.”
Hannah McLeish was one of the motorists forced to reverse from the barriers after realising the system had changed.
She said: “There should have been more warning.
“I’m now going to have to find somewhere to park for free because I can’t afford for it to come out of my wages.”
In a statement posted online, the council said: “The entry and exit barriers at the South Inch Car Park will be in operation 24 hours a day.
“Drivers wishing to use the car park outwith the charging hours need to take a ticket when entering the car park.
“Any drivers who arrive during the charging hours but leave after 6pm will only be charged up to 6pm.
“The 24-hour operation will be reviewed after three months.”