Campaigners battling to keep a new Lower Thames Crossing away from Gravesham’s countryside insist such plans will not help traffic in Dartford.

Highways England has recommended a new crossing east of Gravesend — dubbed Option C — in order to draw some of the motorists away from the often congested Dartford Crossing.

The Lower Thames Crossing Association — set up to fight the plans — believe the Gravesend crossing will fail to prove an effective long term solution.

Spokesman Bob Lane said: “If Highways England get their way, the long-suffering residents of Dartford will still have the same misery of congestion and pollution, even after a new crossing east of Gravesend is built.

“This will give Highways England all the excuse they need to then build a new bridge at Dartford.

“We believe that a tunnel putting M25 traffic underground from south of junction 2 to north of junction 30 is by far the best option for road users and for the people of Dartford.”

The estimated cost of the long underground tunnel is £6.6 billion, compared to up to £5.9 billion for Option C.

Mr Lane also questioned Highways England over figures used to justify its preference for the Gravesend crossing.

He continued: “In 2013, the estimated cost of a new bridge at Dartford was only a third of the cost of a new crossing east of Gravesend.

“If Highways England get their way, the long-suffering residents of Dartford will still have the same misery of congestion and pollution, even after a new crossing east of Gravesend is built" Bob Lane

“By 2016 the cost of a simple bridge at Dartford had spiralled to 90% of the cost of a new crossing east of Gravesend.

“At the same time, the benefit/cost ratios for Gravesend, which are supposed to be a measure of value for money, had mysteriously increased by 100% despite there being no material changes to the costs or benefits.

“Many people think that the costs and value for money ratios have been deliberately manipulated to justify Highways England’s preferred option.”

Mr Lane and fellow campaigners have called on the National Audit Office (NAO) — which audits major transport projects — to scrutinse the figures.

A spokesman for the NAO said the issues surrounding the Lower Thames Crossing will be looked into to ensure it represents full value for money.

Last month, Dartford council urged Transport Secretary Chris Grayling to make an early decision on the crossing, primarily based on the town’s ongoing traffic and congestion problems.

Dartford Labour leader Cllr Jonathon Hawkes also stressed the importance of working to improve air pollution in the town.

The government is expected to announce its preference for the new crossing later this year, but the project is unlikely to come to fruition until 2026.