The Tories are clutching at favourable opinion polls "like a baby grasps for a dummy", Lord Tebbit, the former Conservative chairman claimed yesterday.
In a direct warning to party leader David Cameron, he said Tories were now "in danger of missing the electoral opportunity of a lifetime".
Lord Tebbit, writing in the Spectator magazine, said that no-one seemed to understand the scale of humiliation heaped on the Conservatives and Labour in last month's by-elections at Bromley and Chislehurst and Blaenau Gwent.
At Bromley and Chislehurst, the Tory majority fell from 13,342 to 633 at the byelection, and at Blaenau, a supposedly-impregnable Labour stronghold, the seat went to an Independent candidate for the second time running.
Lord Tebbit said: "The Conservative Party clutches favourable opinion polls like a baby grasps for a dummy. But the polls are all too much like the witches who hailed Macbeth as 'Thane of Glamis, Thane of Cawdor and King thereafter'."
He went on: "In the Tory camp, Mr Cameron has been doing his best to distance the Conservative Party from both its bedrock core vote and its four million or five million estranged former voters.
"The Modern Conservatives give the impression that respectable working- and lower-middle-class supporters in the suburbs, country towns and villages are not quite good enough for the new 'A' list, Notting Hill party.
"The strategy seems to be aimed at persuading Liberal and Labour voters that the Cameron party shares their beliefs and aspirations and would deliver Blairism where Blair has failed."
Lord Tebbit said that the Bromley by-election suggested that while Conservative voters did believe that the new Conservative party was unlike the one they used to support, Mr Cameron's target Labour and Liberal voters did not, "and the Tories are in danger of missing the electoral opportunity of a lifetime".
He went on: "The Blair government is failing on every front. Like a victim of Ebola fever, the vital organs of government are ceasing to function.
"It can tax and it can spend - but it is unable to deliver. There is a deep longing for something better, but it has to be a lot better than what is on offer today."