The Foreign and Commonwealth Office has posted information for travellers about passing through Calais in light of the ongoing disruption to cross-Channel services.
It is urging Brits to check online with operators to get updates on the impact of industrial action and migrant activity in and around the French port.
It also suggested considering alternative routes for going to and from France.
It said the Government was working closely with the French government to seek an urgent return of normal services and has increased security and border force operations at the port.
"The government’s COBR emergency committee has met to discuss the situation in Calais and review implementation of our contingency plans," it said.
"Law and order in and around Calais is the responsibility of the French authorities, but the UK continues to work with its French counterparts to strengthen the security of the border to stop migrants entering the UK illegally."
It said additional border control staff and sniffer dogs have been drafted to France and screening checks have been stepped up at Dover.
"This is on top of already rigorous border controls, which include 100% freight screening at Coquelles and Calais," it said.
It said more than 39,000 attempts to cross the Channel illegally were prevented in 2014 to 2015 – more than double the previous year.
