The incident at the Lowther Hotel in Goole, East Yorkshire, is the first time damage has been caused to the age-old portico - which has remained intact since 1824, even surviving a World War One Zeppelin bombing raid.
But it was no match for the street sweeper which was trying to fit through a gap between the pillar and a nearby 4x4 car.
A structural engineer who has been inspecting the damaged portico estimated the cost of fixing it to be between £5,000 and £10,000.
Hotel manager Rik Duckworth, 27, said: “I looked at the CCTV and I was amazed at what I was seeing and I didn’t know whether to be angry, upset or just laugh.
“If the sweeper would have twisted the pillar by another three inches, the full portico could have collapsed and crushed anything in its path.
“The incident was not brought to our attention for another 40 minutes, and we had around 50 guests arriving for breakfast meetings walking under the entrance. It could have been catastrophic.
“I phoned the police who cordoned off the area and I looked through the CCTV to find it was a road sweeper.
“I was angry to see that the sweeper had just driven off without any apology given at the time. There must have been some force and power behind the sweeper to cause the pillar to twist.”
East Riding of Yorkshire council says the matter is with its insurance company.
The street sweeper was operated by the East Riding of Yorkshire Council, and they apologised in a statement for what it called ‘a regrettable incident’.