Plans for a contra-flow along the M20 as an interim solution for Operation Stack could take two weeks to deploy, it has emerged.

Highways England has confirmed that among the options under consideration for a contraflow is one that could involve a moveable barrier - but that it could take up to a fortnight to set out whenever it is needed.

And in other unwelcome news, Kent County Council says the interim plans are “not sufficiently advanced” to be ready in time for Brexit next year and a permanent lorry park is unlikely to be built before 2023.

Kent County Council transport chiefs have warned the new version of Operation Stack - dubbed Operation Brock - could cause “massive disruption.”

The contingency plan was set out by ministers in May alongside a wider consultation on a permanent lorry park.

Highways England said in a statement: “We are developing a design for the temporary solution and have asked our suppliers to provide a design that can be deployed within two weeks.

"We will work to minimise the impact to road users during this deployment, this includes minimising road closures where this can be done without compromising safety.”

“The solution will involve a contraflow system with traffic using the London-bound carriageway with slow moving freight traffic using coast bound, between junctions 8 and 9.

"The solution is currently in the development stage. We will provide more detail when designs are finalised towards the end of the year.”

The agency stressed that several options were being examined.

But Kent County Council officials have told MPs the contra-flow has the potential to risk “massive disruption” to both local and strategic traffic.

The warning comes in a submission by the council to the cross-party transport select committee, which is carrying out an inquiry into the impact of Brexit on the freight industry.

KCC said in evidence to the committee there was a risk the new solution could prove just as disruptive as the current arrangements:

“Any plan to hold HGVs on the M20 while also allowing non-port traffic to continue to travel in both directions will significantly reduce capacity on the M20 with a contraflow on the London-bound carriageway for non-port traffic between Junctions 8 and 9, and the likelihood of a 50mph speed restrictions.

"This may result in the kind of massive disruption to both strategic and local traffic that is suffered with the existing arrangements for Operation Stack.”

Cllr Mike Whiting (Con), KCC cabinet member for transport, said: “The government has not yet set out fully what it wants; there does appear to be a lack of detail and we have some serious concerns about the proposals.”

KCC has also highlighted to MPs that it could take years to build a lorry park as a permanent solution to Operation Stack, saying: “We are disappointed the completion date of any such scheme, if it is taken through the Development Consent Order (DCO) process, is now likely to be 2023 at the earliest, eight years after the Government’s commitment in the Autumn Statement of 2015 to deliver a solution 'at pace'”.

The potential setbacks are underlined in a separate report due to be considered by county councillors next week.

It says: “KCC is also concerned that Highways England’s plans for the temporary solution to Operation Stack do not appear to be far enough advanced to be ready in time for the UK’s exit from the EU.

"It is essential that a solution is in place that enables the M20 motorway to remain open in both directions with sufficient capacity to allow effective flow on the Strategic Road Network and maintain freight fluidity through the Channel ports.”