Campaigners have renewed calls for a second Brighton mainline rail route, which they say would reduce "bottlenecks" at East Croydon.

It comes after a Network Rail study found the proposed route, which would run from the south-coast city to London Bridge through Crowborough and Oxted, would be the fastest alternative to the current mainline.

Earlier this year, Chancellor George Osborne committed £100,000 to studying the viability of the extension, which campaigners say is essential to reduce overcrowding.

Network Rail's Sussex Study found Brighton Mainline 2 would allow travel from Brighton to London Bridge in 73 minutes, 17 minutes longer than the existing mainline.

The current alternatives to the mainline take between 90 minutes and two hours.

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The proposed extension

A statement from the Brighton Mainline 2 Project Group said today: "BML2’s diversionary capability is just a bonus – because it’s a hugely-useful new main line in its own right avoiding bottlenecks at East Croydon, London Bridge and Blackfriars.

"Instead, Network Rail and the DfT intend over-cramming the Brighton Line. Today’s carriages typically carry 99 people, but the new Thameslink trains will have fewer seats and loads more standing room – carrying half as much again. But they will also be subject to the same old delays and cancellations."

Campaigners envisage the Brighton Mainline 2 would include the creation of a "Croydon Gateway" station -  possibly amalgamating Purley Oaks, Sanderstead and South Croydon - to provide an interchange with the current mainline.

But Croydon Central MP Gavin Barwell said in July the extension would not ease congestion to the north of East Croydon and would disrupt the tram network.

He added: "The priority should be to improve the existing Brighton Mainline and not Brighton Mainline 2 which I don’t believe would alleviate the core issues facing Croydon commuters."

A Department for Transport spokesman said: "We know the importance of good rail links, which is why we are investing record amounts in building a world-class rail network as part of our long term economic plan.

"We continue to look at the options for improving capacity between Brighton and London, and further updates will be provided in due course."