Direct trains between the Midlands and London which call at local stations will be cut from the end of September.
Silverlink's service from Euston will travel only to Northampton and Central Trains will take over the rest of the route to Birmingham New Street.
Fewer stopping trains are seen as an important part of the multi-million pound West Coast Main Line revamp.
Silverlink's trains shadow Virgin's fast service between Birmingham, Rugby, Coventry, Milton Keynes and Euston.
Passengers will still be able to use Chiltern Railways which operates direct rail services between Birmingham Snow Hill or Moor Street and London Marylebone.
The journey takes about two hours with fares said to be comparable to Silverlink and starting at just £15 return.