South London's main rail operator today said it said was planning the "biggest timetable shake-up" in a generation after coming under fire for delays caused by strikes and staff shortages.

Govia Thameslink Railway (GTR) said it wants to boost capacity and "completely recast" many new connections in the south of England to London as well as Bedford, Peterborough and Cambridge.

Govia's Southern franchise has been hit by months of delays and cancellations caused by strikes over changes to the role of conductors and high levels of staff sickness.

GTR said the planned changes from 2018 will lead to greater reliability on Southern's inner London services, new Thameslink services from Kent and a "massive increase" in Thameslink trains at London Bridge.

Phil Hutchinson, who is leading a public consultation for GTR on the plans, said: "We are proposing a complete redesign of the timetable by looking at which journeys are most important to passengers.

"We are creating more capacity and new cross-London routes with connections to Crossrail and more punctual and reliable services.

"Operationally, each route would be self-contained so that if a problem occurs it does not affect other routes.

"We want passengers and stakeholders to help us shape their future train service so we are consulting, we think, earlier than any train operator has before.

"This is a real opportunity for passengers and stakeholders to get involved in an open, honest and transparent conversation about what the train service should be in the future.

"This is about creating better connections and more capacity. It's a once-in-a-generation opportunity to restructure the timetable to give passengers more trains and the much better reliability we all want.

"Ultimately this will put the Thameslink route at the heart of the UK rail network."

Mick Cash, general secretary of the Rail, Maritime and Transport union, said: "Passengers don't want to be consulted on how services may improve in almost two years' time. They want action now to end the daily chaos to their journeys.

"This can only raise suspicions that the Southern spin machine is at full tilt to obscure the reality of cancelled train services and their plans to get rid of guards in their bid to put profit before safety."

A spokesman for the Association of British Commuters, which is raising money to take legal action over the Government's handling of the Southern franchise, said: "The 'new timetable shake-up' is yet another smokescreen from GTR, expressing merely the intention to normalise some trains and timetables.

"We distrust entirely GTR's ability to provide improvements when it is already clear that the company has failed to provide the level of service required under the franchise agreement.

"GTR has collapsed due to long-term and entrenched mismanagement, the true nature and extent of which lies recorded in redacted and undisclosed documents that the DfT (Department for Transport) have failed to release, despite our specific requests for them to do so.

"We are especially concerned by Phil Hutchinson's statement that 'a complete redesign' of the timetable will be premised on 'looking at which journeys are most important to passengers' - where does this leave commuters in more rural communities, many of whom have barely a service remaining?"