They believe the number of trains to the capital from the West Midlands could be cut to prioritise the high speed line, affecting trips between Shropshire and the capital.
HS2 Ltd technical director Andrew McNaughton admitted services could be taken off the West Coast Mainline. He told the HS2 committee in Parliament: "We take off the main line most of the long-distance non-stop services, because the purpose of HS2 is to serve cities on the long-distance network. That means in the peak we see at least 10 totally new services are available in the capacity that we released on the West Coast Main Line."
Mr McNaughton added that the Secretary of State has said that where people have a train service to London, after HS2 comes in, there ought to be a comparable service – but this would be "balanced against the opportunity to improve commuting to the places that most need improved commuting".
Stop HS2 campaign manager Joe Rukin said: "Supporters of HS2 have always said it is needed to 'free up capacity'. We have always said this means for dozens of towns and cities across England, Scotland and Wales losing the trains you currently have.
"Now this has finally been confirmed, it is clear HS2 is not about 'rebalancing the economy', it's about faster journey times to London for businessmen from a handful of cities, increasing the London commuter belt, and delivering £8.3bn of cuts to current rail services from places they don't think are important."