Blue Badge-holders are unhappy because Plymouth City Council is to abandon free disabled parking at the Theatre Royal car park.
They are also complaining that moves to increase the maximum stay in shoppers' car parks from three to four hours fail to take disabled motorists into account.
They want extra parking time for the same money because people with mobility problems take longer to reach the shops and are therefore losing out.
Campaigners handed about 70 protest letters from Blue Badge holders to the city council.
The letters, all worded identically, said: "The council is aware that people with mobility impairments take longer to move between locations.
"It is therefore discriminatory to restrict parking to the same time period as the one being imposed on people without mobility difficulties."
Campaigner Bruce Abbott, of the city's Disability Action Network (DAN), said: "There is no recognition of the additional time disabled people need."
He called on the council to universally install the system in place in the City Market, formerly the pannier market, car park.
That's where disabled drivers can park for two hours when other drivers are restricted to one.
"They have effectively established a precedent," he said.
The protest letters accuse the council of "a breach of duty" to disabled drivers, because it is changing the way it charges motorists at the Theatre Royal car park.
The council is to install barriers to stop so-called 'boy racers' driving around the car park at night.
But it will also mean a 'pay-on-foot' scheme, similar to the one at Drake Circus mall, will be introduced. This allows drivers to pay only for time used, but will end free disabled parking because to include this would have been too expensive.
The protest letters claimed the equipment "will effectively prohibit certain groups of disabled people from using this car park".
They said other technology is available which would allow the council to still provide free parking for Blue Badge holders. The DAN last year gave a presentation to the council promoting a system similar to London's Oyster Card scheme, where money is paid up front and stored on credit.
The letters said the Theatre Royal changes "must therefore be deemed to be discriminatory towards people with mobility impairments".
They claim both proposals are in breach of the council's duties under the Disability Discrimination Acts of 1995 and 2005.
The letters call for the council to withdraw its proposals for the Theatre Royal car park.
But the city council insisted its parking review was due to be implemented by Easter.
It stressed plans to increase the maximum stay at all city centre shoppers' car parks from three to four hours will apply to all drivers.
"We fully understand some Blue Badge holders may need longer than other drivers to go about their business in town, but we think four hours is enough time," a spokeswoman said.
She stressed all multi-storey car parks have parking for Blue Badge holders with no time limits and there are dedicated Blue Badge only car parks in Courtney Street and at Woolworths West.
Blue badge holders are also permitted to park in any pay-and-display bays and dedicated Blue Badge bays.
The spokeswoman said: "We have gone to great lengths to devise parking tariffs which are as customer-focused and convenient as possible for the broadest possible number of shoppers and evening visitors to the city centre, including disabled visitors.
"The council currently provides free parking to all Blue Badge holders unlike many UK councils."
The Theatre Royal car park's new ticket machines would be at a height accessible for wheelchair-users, but the council conceded the system would not cater for all disabilities.
The authority said that if "a small minority" found the system difficult to use, staff will be on-hand to help.
This Is Plymouth, 20th Februay 2009