No attempt has been made to force The Vestry to close early, even now flats are to be built next door.
The bar is licensed to open until 2.30am at weekends but an older planning restriction says it must shut at midnight.
Bar manager Charlie Rose said:“We are not going anywhere without a fight.”
More than 1.000 people have signed a petition in support of the venue’s late hours.
The Vestry is located in the area of the city nicknamed ‘#Chibiza’.
Landlord Jaspar Group has recently been granted permission to build flats in the former Argos building (see below).
The company has consistently said The Vestry must abide by the planning restriction and wants the council to enforce it.
Bar manager Charlie Rose said: “It doesn’t seem right to all of a sudden, after ten years, say you can’t have it any more.
“A lot of people have been really supportive of us. Thank you to all of them.
“We are not going anywhere without a fight.”
Asked about permission being granted to Jaspar Group to develop the former Argos store into flats, Charlie said she does not think it will cause problems for The Vestry but she added: “If it does affect us then RIP to Chichester’s nightlife.”
Jaspar Group development director Lance Calder said: “We are pleased the decision has come through to redevelop the Argos building.
“Obviously the activities of The Vestry were considered by the council and appropriate conditions attached to the consent to ensure the amenity of future occupiers are protected.
“I have seen the petition, for me this carries limited weight in a planning context when deciding the lawful or appropriate future use of The Vestry.
“Any decision will need to be weighed against the relevant development plan policies or planning law as appropriate and should not be swayed by politics.”
A Chichester District Council spokesperson said: “Our planning enforcement team has been investigating and they have alerted the operators of the planning conditions that control the hours of operation.
“Enforcement action is not proposed at this time because the circumstances of the use remain under investigation.”