A cross-Channel ferry will be out of action for a week after it crashed into a harbour wall at Dieppe.

French police and operator Transmanche Ferries have launched an investigation.

After the collision, police are understood to have breath-tested the French first officer, who was at the helm of the 17,500-tonne Newhaven-Dieppe ferry.

The MV Dieppe, which is believed to have a 2ft hole in the hull above the waterline and had 123 passengers on board at the time of the accident, is undergoing repairs expected to take at least a week.

This will reduce the number of crossings by conventional ferries on the 64-mile sea route from four a day to three.

Steve Forrest, the Newhaven- based operations manager of Transmanche, said: "We have launched an investigation and the police in Dieppe have launched theirs.

"We have not yet been notified of any police findings. No one was injured in the incident."

Mr Forrest added: "This is the first time there has been an allegation of this nature.

"We operate a very strict no- alcohol policy for our staff and any violation will mean instant dismissal. If I am invited to the captain's table during a crossing I know no alcohol will be served."

Lewes Liberal Democrat MP Norman Baker, whose constituency includes Newhaven, said: "This is a very worrying incident.

"We have a right to expect that those in charge of public transport vehicles, whether trains, buses or boats, are qualified, well-trained and above all sober.

"This incident could have been far worse.

"The French authorities need to establish very clearly what happened and the ferry operation needs to review its procedures to find out how this could have happened and to stop it happening again.

"Incidents like this only harm the reputation of the line."

At first it was thought the MV Dieppe would be out of action until the end of this week but officials have now confirmed she will not sail until the end of next week at the earliest.

A temporary repair has been made and the vessel is sailing under its own power to the French port of Le Havre to have a new section of hull fitted.

Transmanche, which has two vessels operating on the Newhaven route, has arranged for MV Dieppe's sister ship, the 12,000-tonne Sardinia Vera, to make extra crossings.

The accident, which happened at 1.15am on Saturday, has not affected crossings operated by Hoverspeed, which runs a fast ferry service on the same route.