A new survey has found that properties up to 1.5 miles away from the line are still suffering losses to their value of up to 30 per cent, while those that would be on, or very near, the track are proving extremely tough to sell.

And the blight is not just affecting homes on the preferred route near Aylesbury – properties on the alternative line, which cuts past Risborough and Haddenham, have also been badly hit.

The report was compiled by the HS2 Action Alliance, headed by Hilary Wharf, a rail management consultant.

"Individuals who are affected by substantial percentage reductions of 15 to 20 per cent, most of them do not qualify for the exceptional hardship scheme," said Mrs Wharf.

She said one of the most surprising findings of the study was the prevalence of 'institutional blight' which is compounding the problem for homeowners.

Mortgage lenders are fearful of HS2 exposing them to the risk of negative equity and are instructing surveyors to take the line into account – particularly if it can be seen or heard.

The report adds that lenders, surveyors and solicitors 'typically subscribe to the view that routes commonly change at the margin, so a final route may differ from that initially planned'.

"The behaviour of lenders and supporting professionals is itself spreading blight over very wide areas, through processes of searches, valuations and mortgage lending," states the report.

However, the study also found that solicitors' searches of local authority property databases differ wildly with relation to HS2.

A search by Bucks County Council highlights all three routes, whereas Warwickshire makes no reference to the existence of even the preferred line through the county.