Senior Tories have raised fears about the flood risk associated with the controversial £42 billion HS2 rail line after areas along the route suffered in the recent storms.
Former Cabinet minister Cheryl Gillan said it was "totally unsatisfactory" that a full assessment of the risk had not been carried out.
And Europe Minister David Lidington has written to his Government colleague Transport Secretary Patrick McLoughlin saying the line will concrete over farmland which currently serves as natural flood protection for his constituents' homes.
Mrs Gillan, who has been a vocal critic of the HS2 project which will run through her Chesham and Amersham seat in the Chilterns, said the scale of the project would amount to the same footprint as "many, many houses" in flood-prone areas.
In response to a parliamentary question from Mrs Gillan last month about the risk of the route being flooded, Floods Minister Dan Rogerson said: "The safeguarded area for phase one of HS2 crosses just over 100 watercourses, each of which will have a degree of flood risk associated with them.
"The scale of that risk will depend on the precise alignment of the route. At present this has not been fully assessed, nor has an assessment been made for the phase two routes."
Mrs Gillan said: "This is totally unsatisfactory. You would have thought that was a basic part of any environmental investigation."
With the Government refusing to publish the Major Projects Authority review of the scheme, she added: "You begin to worry what the risks associated with this development are."
She said ministers were fond of comparing the project to the industrial schemes of the Victorian age but "we are not dealing with a country as sparsely populated or as empty as the days when the Victorians built their lines".
In his letter to the Transport Secretary, Aylesbury MP Mr Lidington wrote that the Willows area of the town, which lies close to the HS2 route, was flooded.
" You will not be surprised to hear the residents are very fearful that the construction and operation of HS2 across the floodplain close to their homes will add significantly to the flood risk," he wrote.
"It is indisputable that both construction and operation will require farmland to be taken which for now soaks up surface water and which ought to act as natural flood protection for my constituents.
"People in this part of Aylesbury are sceptical about the assurances from HS2 that they will design in effective flood protection measures."
HS2 Ltd spokesman Ben Ruse said: "During the recent wet weather we have been carrying out visual inspections where the planned line between London and Birmingham crosses watercourses.
"We will continue with these types of surveys where access has been made available as part of the route development.
"HS2 will be designed to remain operational during a one in 1,000 year flood event. Put simply, that means the railway is being built so that it can withstand just the sort of extreme weather that we have seen up and down and the country recently."