One of the longest bus routes in Sussex is again being investigated because of complaints about late running and cancellations.

It could result in fines for its joint operators Brighton and Hove Bus and Coach Company and Stagecoach.

There have been complaints in the past about the 712 route between Eastbourne and Brighton, especially in the evening when the service is run by Stagecoach.

Passengers once objected to being left for three hours at bus stops waiting for a bus to arrive.

There have also been concerns about buses being late and rarely running to timetable in the daytime.

For the first stage of the latest investigation - the second this year - officials from the Vehicle Inspectorate spent three days monitoring the reliability of the service, which should take one hour and 18 minutes to complete its route.

The monitoring was done without prior warning to the bus companies.

Bus drivers say the results will be distorted as the survey was carried out at a time when there were major roadworks in Newhaven and on the A27 at Falmer, which forced more traffic on to the already busy South Coast road, along which the 712 travels.

The service is supposed to run every 15 minutes during the day with buses supplied by Brighton and Hove Buses and Stagecoach.

Stagecoach takes over at 7pm with a half-hourly and hourly service.

The South East Transport Commissioners have now asked Brighton and Hove Buses and Stagecoach to submit comments about a report based on the investigation.

The commissioners will study the feedback and a spokesman said: "We will then decide what action we should take.

"The main thing is whether the buses are running to timetable.

"We have the power to impose fines if we find any bus company is not operating the route as it should."

Phil Medlicott, operations director for Stagecoach, said: "We have taken steps to improve the service by putting dedicated buses and drivers on the route.

"There was a survey in June, suggestions were made and we reported back.

"Reliability has now improved by 20 per cent. In recent weeks we have had difficulties with roadworks in Newhaven."

Roger French, managing director of Brighton and Hove Buses, said: "We have had no complaints about the 712 service.

"If our buses have been late, most passengers have understood it is due to the roadworks.

"I know Stagecoach had problems with staffing levels some time ago.

"We have been asked for our comments on the running of the service and will be reporting back to the commissioners."