Thanet council says measures have been put in place over fears of excessive HGV traffic along Military Road and Royal Parade during an eight week closure of the tunnel to the port.
Essential work is being carried out on Royal Harbour Approach Road by Southern Water, which started on March 5 and runs until May 7.
The closure, which is in phases along the entire length of the road, is to allow permanent reinstatement works following earlier sewer works, being carried out by Clancy Docwra working with Southern Water.
A Kent County Council notice says the alternative route is via A255 Canterbury Road East, B2054 London Road, Grange Road, St Augustine’s Road, Paragon, Royal Parade and Military Road.
The notice adds: “Due to the nature of these works, it will not be possible to re-open the road outside the working hours.”
Conservative Councillor Paul Messenger says the closure will mean “car transporters driving through the town.”
He added: “Thanet council has assumed that the town will put up with it, they are losing money at the port so are focused on any revenue.”
Cllr Messenger added: “I am informed that Seaborne are ready to start their new freight ferry service – which Jan Allaert of Port Ostend cannot confirm- within this port road closure. The recent planning application approval for a lorry park at the port also raises the question of increased HGV traffic through the town.”
HGVs using the stretch by the Paragon may also put further strain on the corroding structure of the West Cliff Hall which supports the main road to the harbour and the first 40 metres of the West Cliff Promenade.
Thanet council says the timing of the work was brought forward to ensure completion before the Summer and businesses on Military Road were visited by the contractors on behalf of Southern Water.
Ramsgate Port will remain open throughout the works and businesses at the port are aware of the programme.
GEFCO car shipments, which may use the port when Sheerness is full to capacity, and Vattenfall heavy load deliveries due to be transported to Richborough “have been programmed to ensure the work will not have an impact,” said a TDC spokesman.
The 90-space lorry park at the port, approved in January, will not open until after Southern Water completes the work at Royal Harbour Approach.
The council spokesman added: “The temporary diversion along Military Road will provide the required access for programmed and anticipated port business to operate for the duration of the works.
“The roundabout is subject to routine safety inspection by Highway Inspectors and any safety critical defects identified will be repaired by KCC Highways. If, residents and road users become concerned about the condition of the road surface during the works, they can also report potholes to the county council via their website and reactive inspections and repairs will be arranged.
“Regular communication will be maintained with local stakeholders and businesses throughout this period to keep any impact to a minimum.”