The axe is poised to fall on the West Midlands' busiest commuter line as part of a wider Government programme of local train service cuts.
The Cross City line - which annually carries 8.5 million passengers through Birmingham between Redditch in the south, New Street Station and Lichfield to the north - currently runs a "turn up and go" frequency of six trains an hour.
However, the Department for Transport has asked train operator Central Trains to calculate how much the line would cost with just four trains running hourly.
The Birmingham Post understands that there would be little financial saving to be made with service cuts and suspicions are growing that the Government's motive is to create more track room for intercity trains at the expense of local commuter services like this one.
The region's Passenger Transport Authority and its executive Centro have pledged to fight any Cross City cuts after winning the six-train frequency in tough negotiations with the Government in
Following the huge increase in Virgin CrossCountry trains in 2002 - and with its West Coast relaunch 11 months ago - the level of service on the Cross City line has been criticised by national rail bosses who view the slower services as getting in the way of the faster intercity trains.
A report to be considered by PTA councillors next Monday states: "They (the DfT) have advised that they will be asking Central Trains to
separately cost a four-trainsan-hour and a six-trainsanhour service on the Cross City line, and have stated that 'there will need to be a discussion between DfT and Centro regarding funding of these additional services'."
Last night, a DfT spokesman said the extra two trains an hour had not been part of the original franchise agreement and had been paid for with Rail Public Partnership funds, which run out in April.
He added the department was simply obtaining a "quote" to see how best to proceed with the line.
A Centro spokesman said: "If this is a serious suggestion we will have to have serious discussions with the DfT.
"The 'turn up and go' level of service is important, not just physically, but psychologically in promoting public transport to more people.
"We would obviously be opposed to any reduction in frequency."
A spokesman for Virgin Trains said: "We don't know anything about this but it could be the Government are asking ' do we need this number of trains on this line?'
"It may be a capacity as well as cost issue because the shortage of capacity at New Street station means that a minor problem can soon have a major knock-on effect."
Alan Bevan, from passenger watchdog Midland Rail Future, said: "It is a very worrying development and would be a big retrograde step for passengers in Birmingham."
Recent reports have suggested Whitehall is drawing up plans to introduce wideranging cuts in local train services to clear the tracks for more high-speed trains and to increase the amount of freight carried.
The first closure proposal under the Government's new Railways Act, the Wolverhampton to Walsall service, was announced on the last day of Parliament.
Despite local opposition, the service will be replaced with coaches next year.
A working paper from the now defunct Strategic Rail Authority also reveals that civil servants are examining a much larger list of service withdrawals across the country.