Rail passengers face fresh travel misery because of a strike by conductors amid claims that the Government is authorising train cancellations.
Members of the Rail, Maritime and Transport union on Southern Railway will walk out in a long running dispute over the role of conductors.
Southern's services, including busy commuter trains into London Victoria, have been disrupted for weeks because of industrial action and "unprecedented" levels of staff sickness.
Commuters in Brighton staged a protest at the station last night against a background of announcements of delays and cancellations to services.
The RMT claimed it has evidence that civil servants at the Department for Transport are authorising cancellations to services run by Southern's owners, Govia Thameslink Railway.
The union said it had seen correspondence between the DfT and Govia it claimed showed the Government was authorising cancellations.
General secretary Mick Cash said: "The Government are up to their necks in the chaos on Southern and not only are they turning a blind eye to the abysmal service being offered to the public, this leaked correspondence shows that they are directly orchestrating it.
"That can only be because they have a wider agenda to force confrontation and chaos on these routes as part of some scam to blame the staff, bulldoze through cuts to jobs and safety and break the unions.
"Passengers are caught in the middle of this scandal and there needs to be a full Parliamentary inquiry.
"RMT's dispute is not with the passengers who suffer the daily misery of incompetence, arrogance and racketeering on the Southern rail routes. Our dispute is with the company who, with the connivance of the Government, have declared war on passengers and staff alike."
Rail Minister Claire Perry said: "It is clear that the current situation on Southern and Thameslink routes is unacceptable and that passengers deserve a far better service.
"The operator is not being let off the hook and the rail franchise agreement contains clear penalties and incentives so that they are penalised for repeated poor performance.
"However, the situation has been made worse by unjustified industrial action. The Government is investing £2bn in state of the art trains, fully equipped with the latest technology and with more space for passengers, including 115 new Thameslink trains.
"These will be introduced this year without any job losses, and it is unacceptable that union bosses continue to overlook the impact they are having on passengers. I urge the unions in the strongest terms to work with the operator to resolve this issue as a matter of urgency."
Southern said a restricted service will be in operation on Tuesday, with many routes having a reduced service, and on some routes there will be no trains at all.
On some routes, services will start late and finish early, so passengers were advised to check before travelling.
"We apologise to our passengers for the disruption this will inevitably cause," said the company.
Southern said the strike was "completely unnecessary."
A Govia spokesman said: "Whilst industry rules require any timetable changes to be agreed with the Department for Transport, it is absurd to suggest the Government ever arbitrarily order any train cancellations.
"The correspondence relates to options being considered should the current high-levels of staff sickness continue although, in the event, the timetable change did not take place.
"The whole discussion was only necessary due to the remarkable 100% increase in conductor sickness, and 40% increase in driver sickness, that has taken place since the strike action began."
A Transport Department spokesman said: "We are clear that GTR passengers are not getting the service they deserve, and it is nonsense to suggest that we order operators to cancel services, we are seeing similar strikes by RMT in Scotland right now on this exact issue.
"Due to the unjustified industrial action on the network, the operator has to consider timetable changes so as many services as possible can run. When this happens, operators are contractually obliged to inform us in advance, but these decisions are taken only when there is no other solution, and this does not amount to the government ordering cancellations."