Visitors to Ashton Court reportedly face no action if they choose not to buy a parking ticket.
A source told Bristol Live the £1.20 daily fee to park at the attraction's Mansion House car park, in Kennel Lodge Road, is "unenforceable".
He claimed Bristol City Council does not have a licence to charge those who do not pay for parking when they visit the country house and mansion.
"That's why they don't allow parking wardens to ticket cars," he said.
"All the parking machines are active and lead the public to believe you have to pay to park."
The council declined to comment on the claim.
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A notice in the Mansion House car park reads: "Infringement of the conditions of parking will incur a penalty.
"A charge of £70 will be issued for contraventions of parking requirements (reduced to £35 if paid within 14 days of the issue of the parking charge notice).
"Failure to display a valid ticket will result in a parking charge notice being issued.
"Unpaid parking charges will be passed to our debt recovery agent at which point an addition £60 will apply."
