Claims made by Highways England consultants that the Lower Thames Crossing could boost the Kent economy by £8 billion and provide 6,000 jobs have been dismissed as “pure fantasy” by one campaign group.

Bob Lane, of the Lower Thames Crossing Association, says no one has yet been able to tell him what the jobs will be or where the revenue will come from and claims the figures have been conjured up to justify the £4.4bn-£6.2bn cost.

The crossing would connect the M25 in Essex and the A2 near Gravesend and Highways England has said it could lead to further growth in housing and support international trade by connecting to the Port of Tilbury and improving transport links to the Port of Dover and Eurotunnel.

But Mr Lane said a study of completed road projects by Campaign to Protect Rural England, established such schemes actually generate far more traffic than they relieve and lead to permanent environmental damage but result in little or none of the promised economic benefits.

He added: “The South East Local Enterprise Partnership should be exerting pressure on Highways England to sort out the problems at Dartford. The Dartford Crossing from Kent into Essex is a complete and utter disaster area, with traffic brought to a standstill 100 times a day to escort convoys of tankers through the outdated tunnels, and accidents and incidents on the approach roads occurring on an almost daily basis.

“Until they have sorted out this bottleneck on the M25 for drivers, businesses, and for the long-suffering people of Dartford, it is sheer madness to even consider putting in another crossing.”

The Lower Thames Crossing is set to open to traffic in 2027, with construction starting in two years time.