Food safety experts said Trents restaurant in South Street was in need of ‘urgent improvement’ after an inspection in November.
The 0 rating out of 5 from the Food Standards Agency is the lowest rating possible for food hygiene and safety.
Inspectors found major improvement was necessary to the ‘cleanliness and condition of facilities and the building’, which includes having appropriate layout, ventilation, hand washing facilities and pest control.
Other major changes needed included checks to ensure food sold or served was safe to eat and evidence that staff knew about food safety.
Improvement was also needed to ensure food was handled hygienically.
The comments were summated by the Food Standards Agency following an inspection on November 21.
Trents is currently the only 0 rated eatery in Chichester.
A spokesman for Greene King, which runs Trents, said: “We pride ourselves on our normally high standards and we apologise to our customers for this unacceptable lapse.
“As soon as we received the report from the council, we took immediate action to remedy the situation.
“Since the inspection in November we have already brought in an entirely new chef team as well as a new manager who started at the beginning of December.
“We are confident in the pub’s standards and are seeking a re-inspection as we hope to regain our previous five-star rating as soon as possible.
“We wish to reassure our guests that we have taken this very seriously, acted immediately and they can enjoy a visit with us with confidence.”