More than 170 people are now believed to have received £100 fines at a poorly signposted Northampton car park - with one early morning gym user reporting 21 separate tickets.
National Car Parks (NCP) began enforcing charges on blue badge holders and introduced an overnight tariff on the upper level of St Peter's Way car park in September.
But as it was previously run by Northampton Borough Council, which allowed for free night and disabled parking, dozens of users say they were completely unaware of the new charges.
NCP has placed signs up detailing the cost to park - but campaigners say they are too small to notice and situated in the wrong place.
And as the car park is operated by a camera - fines are not dropping through drivers' letterboxes until two weeks after the infringement - meaning many regular users are expecting dozens of extortionate penalties for unwittingly parking there on multiple days.
But a campaign, backed by Northampton North MP Michael Ellis, is now gathering momentum in calling for NCP to waive the current fines to date and put a moratorium on further penalties until the signage is improved.
Mrs Websdale, of Weedon, said: "We have 177 in the group now, but I know there are only three or four who have not been fined.
"Of those, we think around 150 are blue badge holders, but I'm now trying to work out how many individual fines there have been, because so many have been fined multiple times.
"NCP is adamant that their signage is okay - but all those people can't be wrong."
Many of those affected by the fines are set to attend a meeting at the Guildhall next week with Northampton Borough Council's cabinet member for community safety, Councillor Anna King.
While last week it appeared that mainly elderly and disabled blue badge holders had been the victim of the poor signage, users of the Pure Gym in St Peter's Way have also told of receiving multiple penalties.
Carol Halloran goes to the gym four times a week just before 8am. But under the new rules, she would have to pay the overnight charge of £2.50 to park there even for just half-an-hour between 7.30am and 8am.
As she parked there for free before, she says she had no reason to approach the pay machine, which lists the charges.
Now she is expecting £1,100 worth of fines after parking there on 11 separate occasions.
"I'm not paying them," she said. "I will take them to court.
"I said I will pay them the £2.50 overnight charge, because they won't allow me to purchase an hour's parking, but that's it."
To add further confusion - up until recently a sticker was placed over the overnight tariff, then removed suddenly without warning when the charge came into force.
One gym user and his wife, who did not wish to be named, and go there nearly every day, are expecting 21 fines between them as a result.
The gym user said: "The thing that gets me the most is that, by law, they have to issue a fine within 14 days. We are receiving ours on the 14th day of each one.
"Surely they must realise something is up when they are issuing the same household with 20-odd fines? Who can seriously afford to pay £2,100?"
MP Michael Ellis has written to the chief executive of NCP Jo Cooper, urging the company to "cancel" penalties against all the people fined so far.
He says he is yet to receive a response from the firm boss.
Letters have also been sent by campaigners to the British Parking Association, which advises on car park signage and disputes, and the disability charity Scope, to put pressure on NCP.
A spokeswoman for NCP said: "We have reviewed our signage on this car park, and we are totally satisfied that we have the correct signage to inform all our customers of parking costs, including informing disabled motorists that parking charges apply on this site.
"Signage was installed on the car park in August - well before NCP began issuing PCNs (penalties) to give motorists chance to get used to the rules of the car park.
"These signs clearly state that ‘charges apply’ for blue badge holders and this message is repeated in and around the car park also.
"The blue badge system does not mean that you can assume parking is free.
"When someone is issued with a blue badge it is explained that the motorist is responsible to look at signage when parking in off-street car parks run by private parking operators to see if disabled parking charges apply, and to not assume that they do not.
"Our signage has been approved by the British Parking Association and is the standard signage."