They claim a report which is the centrepiece of a eight week long public consultation on the future of transport in the region is misleading.
The report, which sets out the combined authority's vision for transport from 2018-2040, says a HS2 route between Sheffield and Leeds was 'confirmed' last year.
But, the campaigners say, this is simply not true.
Grant Morement, of the Hooton Roberts and Firsby HS2 Action Group, said: "I just think that the public have a right to know the truth before completing a survey based on false information.
"This link does not exist at the moment and certainly has not been confirmed.
"Many people will be completing the survey believing that they will be able to go from Sheffield to Leeds on HS2."
Grant admits HS2 Ltd do put the link from Sheffield to Leeds on all their maps, even though it is not part of their plans.
But now, the campaigner says the Sheffield City Region are making the same false claims.
The high speed railway, which is now projected to cost Â£56 billion, is forecast to be completed in 2033.
The scheme's original route - which included a station at Meadowhall - was abandoned last year after Sheffield City Council successfully lobbied for a city centre station.
The new so-called M18 route travels further east and includes a spur off the main route serving the South Yorkshire city.
Grant says that part of the area he lives in will be 'massively affected' by the new route - and will lead to more house demolitions and greater environmental impacts.
"Sheffield City Council spent over Â£200,000 of taxpayers money to promote that," says Grant.
"That is why we are stuck with this M18 route now.
"The Meadowhall route would have provided six full speed HS2 trains per hour whereas the city centre station will only get two and they won't even be running at HS2 speeds.
"The new route doesn't work for Sheffield and it doesn't work for Yorkshire."
Mark Lynam, director of programme commissioning at Sheffield City Region, said:“The Government confirmed the HS2 Phase 2b route in July 2017, which included HS2 services serving Chesterfield and Sheffield Midland stations.
“As such the HS2 Route 2b train service specification, which is currently being developed, will include stops at these stations.
“This is also being developed on the basis that there could be services from Sheffield Midland, joining back onto the main HS2 line, continuing up to Leeds.”