By political editor Paul Francis

The Government’s decision to sell off the Dartford Crossing could derail plans for a third Thames crossing, Kent County Council fears.

County Hall leaders are writing to transport minister Lord Adonis seeking assurances that the sale of the crossing, announced by Gordon Brown this week, will not impact progress being made on plans for an additional crossing.

There are fears that anyone private operator interested in taking over the Queen Elizabeth II bridge and tunnel will want assurances that they will not face competition from another crossing and suffer a commercial disadvantage.

Cllr Nick Chard (Con), KCC’s cabinet member for highways, said it was vital that nothing allowed the debate about where a third crossing should be to be undermined.

He added: “We need a third crossing, not least because we know that the Dartford Crossing is completed congested and we are going to see even greater growth in traffic around this area coming into Kent. Our concern is that one of the conditions that would-be operators may demand is that nothing happens on a third crossing for a number of years,” he said.

“We are writing to ask if any conditions will be attached to any sale. Any delay would have an enormously detrimental impact on Kent and traffic problems."

Kent MP and transport minister Paul Clark insisted that the Government remained committed to investigating the prospects of building a third crossing regardless of the sale.

“Our position is very clear. We have to look at the demand and rising traffic levels and we will continue looking at the options for a third crossing, which we laid out earlier in the year. None of that has changed and we have to take hard decisions given the increase in both traffic and congestion,” he said.

Three new possible options for a Thames crossing in Kent were unveiled in May.

They follow a planning inquiry two years ago, which threw out an alternative crossing linking Thamesmead to Beckton.

The proposals on the table are:

• At the site of the existing crossing

• Between the Swanscombe Peninsula and the A1089

• From east of Tilbury to east of Gravesend to the M20.