County transport chiefs say they are likely to back a second Dartford crossing that runs from Tilbury to the east of Gravesend to the M20 - but warn it may have to be a tunnel.

Cllr Keith Ferrin (Con), KCC’s cabinet member for transport, said the council would not support the option of putting an additional crossing at the existing site, saying it would add to already high levels of congestion and pollution.

Of the three options outlined by the Department for Transport, KCC believed the most viable scheme would be one running through to the east of Gravesend.

But Cllr Ferrin said that might only be possible with a tunnel rather than a bridge, which could have to be twice as high as the existing Queen Elizabeth 2 bridge.

It is understood an unpublished report commissioned by KCC to look at alternatives has also come down in favour of a crossing in the same area.

Cllr Ferrin said: "We have been looking at both the options for Swanscombe and east of Gravesend and believe the latter is probably the best option. The Swanscombe peninsula does have the advantage that the river is not too wide and would therefore be cheaper. But we think it would not be as useful to have it there. We want to see traffic diverted away from the north west Kent urban area and that would be right through the middle which is not the best option."

But he added: "In our view, a bridge is not a runner. It would probably have to be 95metres high and that could make it more expensive and in terms of costs, a tunnel would be cheaper."

The county council’s likely support for the Tilbury - east of Gravesend option is likely to put it at odds with Gravesham council, which has already signalled its reservations.

Cllr Ferrin said KCC had already told transport minister Geoff Hoon that it would not back a new crossing at the existing site.

"We are totally opposed to the expansion of the Dartford crossing. We believe it is not a practical solution to the problem and we are dead against it."