MPs from Devon and Cornwall came away empty-handed after pressing Whitehall civil servants to keep threatened railway services.
Commuters are concerned that fast services might be cut
They said the government's minimum service commitment, starting in December, is worse than before.
The number of trains taking only three hours from Plymouth to London, which they say is vital for investment, would be cut from five a day to one.
But MPs were not given any commitment on the services.
Neither were civil servants prepared to offer any promises on services to and from Newquay, or the timetable from Ivybridge, all of which are under threat.
North Cornwall MP Dan Rogerson, said: "The new services do not meet the concerns of the people in Cornwall.
"There are particular concerns about the branch lines and under the new franchise there is not going to be investment to increase the size of commuter trains.
"People who commute in and out of Truro often have to stand and we were hoping for some action on that , but it seems as if there won't be."
Julian Crowe, general manager for First Great Western in the west of England, said the firm was discussing concerns with the Department of Transport.
"But there will be nine high-speed trains from Cornwall to London a day in the new timetable, compared with seven now and some of those trains will replace local services," he said.
"That will include a new service between Newquay and London in July and August.
"We are also investing £100m in improving rolling stock."
MPs will now lobby Transport Minister Derek Twigg and First Great Western, who have the ultimate decision to build on the minimum commitment.
A decision on the level of service is expected from the minister next month.