Work is underway to install a revolutionary concrete barrier along the M20 that could limit disruption to motorists when Operation Stack is implemented.

But drivers have been warned to expect some short-term pain with hold-ups likely until the installation of the so-called Quick Moveable Barrier (QMB) along an 8km stretch of the motorway between junctions 11 at Hythe and 12 at Folkestone is complete.

The Highways Agency says it will take between three and four months to complete the work, which coincides with the busy summer holiday period. There will be lane closures and overnight closures of slip roads on to the motorway and a 50mph speed limit.

The barrier, which can be 'unzipped' from a special vehicle, will eventually be used to implement a contra-flow along the motorway and keep traffic moving in two lanes, avoiding the need to divert it on to the A20 when Stack is in place.

Roads minister Tom Harris said: “I’m very aware of the disruption that Operation Stack causes for people in Kent. Installing this new moveable barrier will help ease that disruption while the Highways Agency continues to work with Kent County Council, the police and other partners to help find a longer term solution.”

As well as installing the new barriers along the central reservation, the work will change the road layout on sections of the M20 between junctions 11 and 12.

The barriers will create a contra-flow on the London-bound carriageway while commercial vehicles heading for Dover are kept on the coast-bound carriageway - with the aim of improving journey times on the M20 during Operation Stack and reducing pressure on the A20 diversion route.

The work will involve changes to the road layout on sections of the London-bound carriageway of the M20 between junctions 12 and 11a to provide space for the barrier. The layout of the entry slip roads on the London-bound carriageway at junction 12 and 11a and the coastbound entry slip road at junction 11 will also be changed.

Ashford MP Damian Green said: "There will never be a good time to do something like this so it is better to just get on with it, however frustrating it might be for motorists. The sooner it is in place, the sooner we can see if it works."