Tom Griffiths, 74, met his friend for a pint at The French Horn, in Market Place, Codnor, on May 28.
But just weeks later, he received a fine from a private company which had taken over running of the car park on instruction of pub owners, Greene King to stop unauthorised use.
Visitors are meant to give the pub staff their number plate to avoid getting a ticket.
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However at the time, Mr Griffiths, who lives in Codnor Park, said there were no clear signs in place and he was never asked to hand his details to staff during his nearly two-hour long stay at the pub, therefore remaining unaware.
“We’ve used this pub for many years and of course it closed down due to the coronavirus,” he explained. “When it opened up again, it had all been done up nice inside and it’s run by really nice people.
"So a friend and I decided to meet up and go for a pint. When we went in we were asked to put our name in the book and our telephone number, we had our masks on and put on some hand sanitiser. We had a couple of pints each that’s all then off we went.”
Mr Griffiths visited The French Horn again a week later, during which he was asked for his registration details.
However, the damage had already been done and he now faces a £100 fine – reduced to £60 depending on when it is paid.
His friend, Phillip Hallsworth, has also been sent a similar fine by car park owners Britannia Parking.
Mr Griffiths added: “I phoned the pub up but they said it wasn’t anything to do with them. We’re not going to pay £100 each for a fine.
“At the end of the day, we’re coming into the pub for a pint, it should have been brought to our attention if there’s a fine in the car park.
"The pub told me they’ve had one or two people have a fine, so it needs bringing to people’s attention.
"If I have to pay this I won’t be going again, not because of the landlady or landlord because the service is excellent. [The fine] is a disgrace.”
Mr Griffiths has since lodged an appeal with Britannia Parking calling for the fine to be overturned as he was in fact a genuine pub customer.
Britannia Parking said it is a member of the British Parking Association and operates in accordance with the industry’s Approved Operators code of conduct.
A spokesman for the company added: “The car park system has been introduced to keep parking spaces available for patrons of the pub as there was a build-up of illicit and non pub related parking during Covid restrictions.
“Customers who park in this pub car park and do not enter their vehicle registration into the kiosk provided on the bar are at risk of receiving a Parking Charge Notice.
“We do not comment on individual cases. However anyone who is issued with a PCN has the opportunity to appeal if they feel there are mitigating circumstances and we recommend this course of action.’
The French Horn has been approached for comment.