The government is to develop detailed plans for two options for a third Thames crossing, it has been announced.

Transport secretary Patrick McLoughlin said the decision would not delay the long-awaited scheme and would allow a proper assessment of how a new payment scheme on the existing crossing was working.

The two options are for a crossing close to the existing crossing - so-called Option A - and Option C, connecting the A2 and M2 to the M25 via the A13.

Transport Secretary Patrick McLoughlin said: “As part of the M25 orbital route around London, the Dartford Crossing is a crucial part of the country’s strategic road network.”

“We are committed to a new Lower Thames Crossing, but whichever location is chosen, it will have a big impact on people in the area and we must make the right decision.”

He went on: “This work will not delay the delivery of the crossing but allows us to choose the best option for local people and the region’s economy, so that it helps boost transport links and economic growth.”

The work will show the range of possible routes at either location and identify their economic, environmental and social impacts, as well as costs.

The decision comes as the Department for Transport publishes its response to the public consultation on location options for a new Lower Thames crossing, which generated more than 5,700 responses.

The government said the decision did not affect its belief that a new crossing would be needed as traffic levels were predicted to increase in the area.

Dartford MP Gareth Johnson has backed the government’s decision, saying it was “prudent.”

He said: “A second Thames crossing is expected to cost up to £3bn, the equivalent of 30 new hospitals and it would be wrong to spend that kind of money without having the full facts.”

He added: “There are so many variables in this decision.

"First, we need to wait and see how the traffic flow changes with the introduction of the free-flow system and the removal of the toll booths in October.

"Only then will we be able to see which of the variables east of Gravesend will work best. It is likely to confirm that we do still need a crossing even after free flow is introduced.”

He added he was “totally against” building another crossing in Dartford, the so-called option A, as it would lead to more of the same traffic difficulties.

“Building a crossing further down the Thames estuary is in my opinion the best alternative for motorists but I accept that we need to see exactly how the traffic will flow after the tollbooths are removed to tell how best to build the roads in that area.

“This decision will not delay the building of crossing, due to be in place by 2025, but we have to make sure we get it right.”