Trade is reeling this week from a two-pronged assault on deliveries travelling through the port of Calais.

A strike by French ferry workers has created huge backlogs of freight traffic on both sides of the Channel.

Kent Police implemented Operation Stack, an emergency measure to park lorries on two lanes of the M20, in Kent, heading for the Continent. As a result, traffic queues stretched for up to 20 miles.

The Freight Transport Association (FTA) said just one day’s delay hit freight operators with extra running costs of £5.5m.

This cost was expected to rise to many millions more in terms of shortened produce shelf life and even further when the continued problem of stowaways breaking into vehicles to secure passage to the UK was factored in.

This was because they contaminated produce which subsequently to be destroyed – a loss of about £20,000 worth of produce per truck, according to the FTA.

James Hookham, the FTA’s deputy chief executive, expected French police to disperse strikers by the weekend, thereby relieving the need to park up freight on two lanes of motorway traffic.

“Nothing’s moved through Calais over the past 48-72 hours so there must be pending shortfalls in stocks and deliveries as a result,” said Hookham on Thursday.

He said UK retailers were refusing to accept consignments breached by migrants and loads were being written off, with insurance not covering everything.

The publication by the Home Office of a list of hauliers signed up to the Border Agency code of best practice on load and vehicle security was believed to be imminent when The Grocer went to press.

“Buyers of haulage ought to start asking questions about the level of security hauliers are applying to their loads, as in the Home Office minister’s [James Brokenshire] view, they are easy to breach,” said Hookham.

“We are suggesting to the Home Office these guys be given some kind of preferential route through the port, because they will pose less of a risk than others.”

Nigel Jenney, chief executive of the Fresh Produce Consortium, said its members were doing their “utmost” to divert shipments via other ports but this was causing delays, as everyone was trying to do the same.

“I had a meeting with James Brokenshire this morning about the stowaways. They are taking the situation seriously and I’m hoping, and realistic, there will be a solution as soon as possible,” Jenney said.

“The industry needs to play a part in encouraging suppliers and chosen hauliers to adopt this guide urgently and have robust controls when and if stowaways are found.”

He also called for the Food Standards Agency to issue clear guidance of what the options were when stowaways were found among food in vehicles.

A British Retail Consortium spokeswoman said: “It is too early to measure the impact, if any, on retailers as the result of recent events in Calais.”