Much has been made last weekend – by left of centre commentators as well as those on the right – of the death of New Labour following the Budget decision to break the defining manifesto commitments, in the 2007, 2001 and 2005 general elections, not to increase the top rates of income tax. None was more forceful or coruscating than that on Saturday by Lance Price, Alastair Campbell's deputy press secretary in Downing Street during the Blair years. He wrote, "RIP New Labour. Born 21 July 1994; died 22 April 2009. Cause of death; drowning in a sea of debt. New Labour passed away surrounded by its family and loved ones. It was survived by a shattered party. Memorial service scheduled for May 2010. No Flowers."

For Mr Price, and others who supported New Labour, the defining reason for its success was the promise not to raise direct taxes. "The promise was central to New Labour's appeal to those who had never trusted the party before and was explicitly repeated in the 2001 election, that I helped to plan, and again in 2005." He went on to describe how it embodied the spirit of the New Labour commitment not to punish success – although "the successful will certainly be feeling punished now".

While Tories are understandably ambivalent about their immediate chances of reversing this increase, they need to understand the burning sense of anger from those that founded, trusted and voted for New Labour precisely because of these tax pledges.

But at this weekend's Conservative spring conference – where no one could doubt the energy, unity, vitality and confidence of the party, the like of which I have not seen for 30 years since Margaret Thatcher stood on the threshold of power – I could not help feeling that David Cameron was also burying what might be described as "Cameroon Conservatism". His "age of austerity speech" could not be more sharply contrasted in tone and spirit from the speeches of his first two years as leader.

Re-reading a compendium of Cameron speeches in 2006 entitled Social Responsibility – The Big Idea feels as if another David Cameron has now emerged from the young pretender who took the party by storm four years ago – pledging then that "the old policies aren't coming back". Here is a flavour from the speech to the Google Zeitgeist Europe Conference in May 2006. "Too often in politics today, we behave as if the only thing that matters in the insider stuff that we politicians love to argue about – economic growth, budget deficits and GDP ... it is time we admitted that there is more to life than money, and focused not just on GDP but on GWP – general well-being."

Many other similar speeches followed that year culminating in his party conference speech in 2006 with the call to "let sunshine win the day".

But, as the economic storm clouds intensify, neither his speech at Cheltenham this weekend, nor that of the shadow Chancellor, George Osborne, could be faulted for their clear understanding of the dire circumstances in which they will assume the nation's destiny in 53 weeks' time. The ghost of Thatcherism even clanked its chains during the proceedings – all that appeared to be missing from both men was a blond wig and a handbag.

Mr Cameron has often been accused, in the past, of wanting to distance his party from the Thatcher legacy. But as the 30th anniversary of the 1979 election approaches, Tories might reflect on last week's YouGov poll for Prospect magazine showing a 47/34 per cent advantage for Lady Thatcher to be Prime Minister again over Mr Brown, and a 49/24 per cent split between her and Mr Cameron.

The question remains whether the present Tory leadership knows precisely, even if they may not be able – or wish to – share beforehand in detail with the electorate, what appalling medicine they will have to prescribe when they take office. Ironically, Mr Osborne was able to turn to his advantage the criticism that he has so far refused to write, in advance, his 2010 budget.

Yet Mr Cameron, is still the same person, if older and wise, as he has always been – with a natural optimism which marks him out, along with Tony Blair, from the dourness of Gordon Brown. So even against the grim economic backdrop through this "age of austerity" which will characterise the whole of his premiership, he will still want to offer hope. Can the policy proposals Oliver Letwin has spent three years working up – during the age of plenty – sustain the Budget demands of a thrifty and miserly Mr Osborne?

Mr Cameron hinted in his call on shadow ministers, to provide "more or less", that he already knows their current promises even on health, education and overseas aid may have to be revised. And he implied that any cabinet minister in his administration would risk the sack if they come to the table with the usual attitude of securing as much for their departments as they can.

Efficiency savings, the cancellation of ID cards and expensive centralised government computer programmes will not alone make more than a marginal impact. And as Steve Richards has frequently noted here, Tory reforms already announced on welfare and education may actually lead to increased start-up costs.

So somewhere the Tories need a huge dramatic economy – a wholesale shutdown of a complete government programme. Even Tory grassroots members – if not all MPs – may be receptive to the consideration of the total abandonment of the Trident nuclear programme; something suggested long ago by Michael Portillo, a former Tory defence secretary.

Many are suggesting that the details can be left deliberately vague until after the election. But this will be the first modern Conservative government to contend with a House of Lords without an inbuilt Tory majority. Any legislative programme announced post election day, other than finance, not specifically included in the election manifesto, runs the risk of being defeated by the Lords. Labour and Liberal Democrat peers will enjoy the first opportunity they have ever had to block the decisions of a Tory government. While we know Mr Cameron's own journey to Downing Street is nearing its end we still need to know where he is taking us.

m.brown@independent.co.uk