Labour councillors at Felixstowe say leaving the European Union could have “grave implications” for Britain’s busiest container port.

While the Port of Felixstowe’s main trade is with the markets of the Far East, it has significant business with European ports, particularly via feeder ship trade when larger vessels off-load goods to be carried to other ports by smaller ships.

Mike Deacon and Kimberley Williams said backing the campaign to keep Britain in the EU was “a fairly straightforward decision” for them.

They said: “We both believe that the country will be more economically stable in the EU than out of it, with potentially grave implications for the future prosperity of the Port of Felixstowe and local jobs if we leave.

“The EU is a ‘customs union’ and therefore a single market, which means that member states do not impose tariffs and restrictions on goods being traded between the members of the union.

“Although China and the United States of America are significant trade partners for the UK, the European Union is the most important source of UK imports, accounting for just over half of all imports into the UK, which are then dispersed both here and re-routed to other parts of Europe.

“We should not under estimate the impact leaving the EU will have on the future prosperity of the port.

“Leaving the EU may impact on our trade relations with other countries, who may give less weight to the significance of the UK as a trading partner.

“The UK is currently part of the world’s largest market, and leaving the EU would reduce it to the sixth largest, a fifth of the size of the current EU.”

The port employs 2,600 people directly while port-related business supports around 10,000 more jobs in the area.

During Prime Minister David Cameron’s recent visit to the port, Clemence Cheng, chief executive officer of Hutchison Ports (UK) Ltd, the Port of Felixstowe’s owners, said: “26% of exports from Felixstowe go to other European Union countries and during his speech Mr Cameron acknowledged that good trading relations are important with all countries to help the UK economy continue to thrive.”