THREATS of terrorist activity at ferry ports in Kent and other parts of Britain have resulted in a step-up in security measures.

Ports have been placed on a high state of alert after sources in France and Holland warned a lorry loaded with explosives was going to try and cross the Channel on board a ferry.

Gwyn Prosser, Dover's MP, a member of the select committee scrutinising anti-terrorist legislation and a former cross-Channel engineer, said: "I'm confident the Port of Dover and the ferry companies are well equipped to respond to the heightened terrorist security alert.

"Since 1990, when I was a serving chief engineer on the Channel, major security measures have been put in place, a special branch unit is attached to the port and there are far more people guarding our borders than ever before.

"Working together with the Dover Harbour Board police, Customs officers and the Immigration Service, the combined level of vigilance is very high.

"In more recent years there's been an increased British security presence on the French side of the Channel to help deal with the problems of smuggling and illegal immigration. So taken as a whole, Dover probably has the tightest security regime of all the UK's ports.

"There will never be such a thing as 100 per cent protection of course, but in my view there is no reason for people to change their travel arrangements or to postpone their Christmas cross-channel shopping trips on the basis of this alert. I certainly won't be."

SeaFrance spokesman Nick Thornton said: "Robin Wilkins, managing director of SeaFrance UK Ltd, has said that the company, along with other cross-Channel operators, fully supported the vigilant security measures at the Port of Dover. We all regard the safety of our passengers as a priority and will take whatever steps necessary to ensure the safety of passengers."

Nick Stevens, of Hoverspeed, said: "We're very tight on security and, although we don't carry freight we're checking cars and passengers at random. We are ever vigilant for the safety of our passengers." P&OStena Line chose not to comment.

It is believed the roll-on roll-off ferry operators were ordered to a level of alert described as "heightened emergency" - the highest state they have been on since the current alert system was introduced - last Friday.

Robin Dodridge, head of operations and security at Dover, said ports around the country had been told "to further tighten up their security levels to Christmas and particularly at this time".

Searching of lorry traffic and other security measures had been stepped up, added Mr Dodridge.