Homeowners on land threatened by the potential construction of a rail depot on land south of Northampton feel they're being short-changed by the developers' offer to buy them out.
Around two years ago residents who seem likely to lose their homes should the Rail Central project go ahead were offered compensation as a property bond.
The bonds did not equal the full value of the house, according to locals, but it meant the homeowners wouldn't lose the entire value of the home.
But campaigners now claim that what residents were originally promised is different from what they have been offered two years later and have voiced their concerns to their MP.
"Several residents have been in touch with me about the property bond that is being promoted by Ashfield Land and their agents in relation to the proposed Rail Central strategic rail freight interchange near Blisworth," wrote South Northamptonshire MP Andrea Leadsom on her website.
"I am deeply concerned by what I have been told by these constituents about the way that they are being treated by Ashfield Land, the lack of communication and engagement, and the costs that are being incurred in simply trying to understand the detail contained within the property bond documentation.
"I am also disappointed that the current property bond on offer appears to be substantially less generous than that which was initially proposed."
The MP has written to Ashfield Land director James Digby to ask for clarification and has escalated the matter to the Secretary of State for Transport, Chris Grayling.
Rail Central though say that the update made to the optional bonds are "not significant and do not fundamentally change the provision of the offer".
"The property bond is a wholly discretionary measure put forward by Ashfield Land and Gazeley in response to an acknowledged gap in the statutory compensation code," said a Rail Central spokesperson.
"It provides much greater protection for those property owners near the site who choose to accept them than is required via the planning process, and than would otherwise be available.
"It is intended to be a positive commitment to working with near neighbours and to give them a guarantee for an independently assessed and fair market price for their property if, subject to Rail Central being consented and work starting on construction, they wish to sell their property.
"It has recently been updated to ensure it is as effective as possible.
"These updates are not significant and do not fundamentally change the provision of the offer."
Campaigners from Stop Rail Central say they asked Mr Digby about the bond at a liaison meeting and claim he responded saying he didn't believe the terms had been changed.
He is later said to have conceded he hadn't read the latest version of the bonds.
"The issue was raised by Stop Rail Central at the July meeting of the local liaison group," added the Rail Central spokesperson.
"We wrote to SRC earlier this week to provide further details and information on how the bond has evolved."
Up until now, campaigners had not had a reply from Ashfield Land and the silence had prompted them to reach out to Mrs Leadsom.