Broxtowe's Labour candidate has said he is prepared to vote against his party on the HS2 rail project if elected.
Nick Palmer, who lost the Nottingham seat in 2010 to Conservative Anna Soubry, said he wanted "more assurances" before he would support it.
Ms Soubry said she was "astonished" to hear he did not endorse the "fantastic opportunity" for the local area.
They were speaking at a live debate on the BBC's Politics Show on Sunday, which included the Greens and Lib Dems.
Mr Palmer, who served as the constituency's MP from 1997 until 2010, said: "The reason I would be prepared to vote against it, if we don't get the assurances we need [is], we've just seen what happens with the tram project, which all three of us supported, it has caused two years of chaos."
Ms Soubry said the benefits of HS2 must not be underestimated.
"I'm absolutely astonished to hear the Labour candidate not being in favour of Toton Sidings, getting the East Midlands hub. This is a fantastic opportunity."
The HS2 route will link London with Birmingham, where it will split to head north to Leeds and Manchester.
The planned station will be to the east of Toton Sidings with high-speed trains able to get to and from London in 51 minutes.
Peter Saull, BBC Radio Nottingham political reporter on Broxtowe
In one of the tightest marginals in the East Midlands, transport is pushing other issues into the slow lane.
The Labour-run city council announced phase two of the Nottingham tram back in 2011 but it has been beset by delays and is now running well behind schedule. It's also become a key concern for many voters.
Broxtowe is a classic Labour-Conservative battleground. The Tory defence minister Anna Soubry had a majority of just 389 at the last election and Labour's Nick Palmer is again contesting the seat.
Stan Heptinstall, Liberal Democrat candidate, said: "I'm totally in favour of it [HS2] because it's the way to go.
"You go to Germany, you look at their infrastructure, you've got these fantastic roads, these fantastic railway systems, the ICE trains, it's a pleasure."
David Kirwan, Green candidate, said: "It's the wrong type of investment and it's interesting to hear that Nick has come out today to say he is opposed to it.
"It's the latest in a string of Labour policies that Nick is opposed to. He is not standing as an independent MP he is standing as a Labour MP."
Other candidates also standing in Broxtowe: Ray Barry (Justice for Men and Boys) and Frank Dunne (UKIP).