Not a penny of the estimated £6.8 billion set aside to build a new tunnel linking Kent and Essex is for surrounding roads, it can be revealed.

Highways England confirmed the cost of the Lower Thames Crossing, a new route under the Thames to be built to the east of Gravesend, is "specific to the scheme".

That includes new junctions connecting surrounding roads to the 14.5-mile route but not those which are not directly connected.

MP says the Lower Thames Crossing "must not be built" without investment in local roads

This is despite a predicted average traffic increase of 5%, equating to thousands of extra journeys a day.

That means already congested routes such as Blue Bell Hill (A229), Detling Hill (A249) and the A228 could be crippled.

As the deadline for a final consultation on the overall scheme approaches one MP has warned the crossing cannot be built until more money is invested in the network.

Tonbridge and Malling MP Tom Tugendhat said: “The Lower Thames Crossing is a good idea in principal, but it is likely to increase traffic on our existing roads by as much as 10%.

"That’s why the crossing must not be built until there is serious investment not just in the M20 and M2, but also roads like the A227, A228, Blue Bell Hill and Detling Hill.

“The consultation offers no solutions to these problems and I have made this quite clear in my response.

"Without investment before the crossing is built, rat runs will be developed and it won’t have the benefits Highways England think it will.”

When asked why the project didn't factor in all affected roads Highways England pointed to several ongoing and upcoming schemes, including a major revamp of Stockbury Roundabout, improving the A2 junctions at Bean and Ebbsfleet and creating a 'smart motorway' between junctions 3 and 5 of the M20.

The 2020-25 programme is yet to be announced.

Implementing other mitigating measures will be down to the responsible local authority, which in the vast majority of cases will be Kent County Council.

KCC has been approached for comment.

A final consultation on the overall scheme concludes at midnight tomorrow (December 20). To comment go click here.

In regard to how much motorists will have to pay each time they use the crossing, Highways England says a decision is one for central government but it is thought the toll will be "broadly comparable" to the Dartford Crossing.

Previously it's been suggested the fee may change to reflect the time of day, with it costing more to use at rush-hour.

Highways England confirmed there will be another consultation before any decision on a toll is made.