CHERYL Gillan admitted this week she thinks HS2 will be given the go-ahead - and the last chance of stopping building work lies in residents' hands.
The Second Reading of the controversial project's Hybrid Bill - effectively its planning application - takes place in the House of Commons next week.
MPs are set to vote on whether to agree to proceed with the scheme and Mrs Gillan is expecting a majority to be in favour.
Once the ballot has taken place residents will be given the chance to petition Parliament - and Chesham and Amersham MP Mrs Gillan is urging as many of her constituents as possible to make their voices heard.
She told the Bucks Free Press: "I don't think we are going to stop it now. There's a doubt whether the MPs can make much of a difference. That's why it's so important to petition and ask for changes - it's up to constituents along the route to petition properly.
"The process is quite complicated - government hopes it will be complicated to put people off."
Residents will have a three week period to petition Parliament and Mrs Gillan said she would raise the issue of the 'ridiculous' timescale during the debate in the House of Commons, which begins on Monday.
She said she would provide advice and information on how to petition on her website - adding she will make sure any representations handed in to her constituency office in Amersham is personally delivered to Parliament.
She said: "They shouln't just oppose it for opposition's sake. You have to make a case for not building it and you have to mitigate and protect your environment."
Mrs Gillan's constituency will be one of the most adversely affected by building work, with the line cutting through the Chilterns Area of Outstanding Natural Beuaty, and she said: "There's no huge support for it apart from those with vested interests. I'm sure they [MPs in favour of HS2] will have lined up a series of speakers to promote the project."
She urged residents to focus on getting the tunnel which will be built through the AONB to be extended, lessening its impact on the environment.