A new opinion poll shows support amongst voters for HS2 is at just 24%, with 55% against the controversial £50bn train line which would cut through Bucks.
The YouGov poll for the Sunday Times comes as the Prime Minister and Chancellor gave their backing to develop plans for HS3, which would connect Liverpool, Manchester, Leeds, Sheffield and Hull and cost an extra £5bn.
Sir David told the Sunday Times that if HS2 was scrapped, a new motorway would have to be ploughed through the Chilterns, while there would also be house building in the south-east as the northern economy would not be as attractive for new homes.
Stop HS2 dismissed his warning as ‘scaremongering’.
The poll shows only 10% of people think HS2 would be good for the environment.
The only party whose supporters think HS2 is generally a good idea are the Liberal Democrats, with 42% being for and 38% against.
Conservative supporters are a net of 17% against (32% for, 49% against), Labour 33% against (24% for, 56% against) and UKIP 52% (17% for, 69% against).
Stop HS2 campaign manager Joe Rukin said: “George Osborne and David Cameron will be in Leeds today at the umpteenth relaunch of HS2 because they have got it in their heads that it is a vote winner, but the polling has shown that support for HS2 started badly and has just kept on dropping and dropping.
“Amongst their own supporters there is a whopping 17% gap between opposition and support, and amongst Labour supporters the difference is 33% between those against and those for this white elephant.
“It seems that with this closed-minded support for HS2 the main parties are just giving people another reason to vote for The Greens or UKIP, both of whom oppose HS2.
“In times of austerity, it is only in the minds of the Westminster elite that this vanity project is seen as a priority. Yet their latest bright idea is to propose HS3, a railway that per mile would be even more expensive than HS2.”
Prime Minister David Cameron said: “Improving connectivity and reducing journey times between our great northern cities is a crucial part of our long term economic plan for the north to boost businesses and create more jobs and security for hardworking people.
“That’s why we are backing HS3.”