Steve Richards: It's the crisis of identity that needs to be addressed – not a change of leadership

At different times, Gordon Brown and David Cameron have claimed ownership of the most potent word in British politics: they seek to be agents of "change". Brown spoke of change repeatedly during his brief honeymoon, a distant fuzzy era that seems to have taken place at least a century ago. After the Conservative Party's triumph in last week's Crewe and Nantwich by-election, Cameron declared with a showman's flourish that the spectacular result was a vote for change.

Change is an inspiring and conveniently imprecise concept. As David Bowie recognised when he built an entire career on being an elusive chameleon, and wrote a brilliant song on the theme, we are all in favour of "Changes". The prospect of a switch from one thing to another is exciting and intoxicating. Vague promises of leaps from the present can also be an illusion. Their deceptive nature take us to the heart of the near-terminal crisis tormenting Labour and which might, at a later period, become a crisis for the Conservatives too. The illusion is exposed when we seek to grab this elusive concept, to hold it for a second or two and ask what is meant by uplifting proclamations of change.

Take a close look and it is clear that Brown and Cameron are trapped for different reasons in the status quo of the Blair era. Neither represents a dramatic leap in new directions. They talk of changes but there is no transformation that compares with Bowie moving from Ziggy Stardust to Aladdin Sane and on to his bleak Berlin period, although the chillingly bleak albums produced in Germany during the mid-1970s would be an appropriate soundtrack for the Prime Minister as he contemplates his current political nightmare.

Brown has failed to personify significant change for several complicated reasons. He cannot disown overtly his predecessor's agenda, which he supported at least in public and in votes in the Commons. He is even more reluctant to do so when the Tories adopt much of the Blairite approach, worried that he will be accused of moving leftwards into vote losing territory. Since the collapse of his self-confidence, Brown is tempted more often to cling to the unchallenging comfort zone of populist Blairism, pretending that choice for all in public services is possible without spending a fortune, building more prisons when the prison population is already too high, hailing identity cards as a way of tackling immigration, boasting that he has fulfilled Margaret Thatcher's dream of cutting the basic rate of income tax to 20p.

There are many progressive policies that Brown pursues behind the scenes, but the chosen public narrative – the items where political capital is being used up – have echoes with the late Blair era. The changes are not obvious, staring in front of our eyes. Brown has not changed into a strikingly new costume.

Nor has David Cameron, the apparent personification of change. His genius was to have an insight that was almost the exact opposite of change. He recognised that, far from being a threat to the existence of the Tories, Blair endorsed much of what they believed. In 1997, voters might have turned away from Thatcherism. On several fronts, Blair brought it back to life.

As they have argued, Cameron and George Osborne are the heirs to Blair. Some Shadow Cabinet members tell me without irony, awkwardness or a hint of mischievousness that they became Blairites during Labour's second term. Far from being agents of change, they support more "choice", possibly with even less public investment, and put the case against the state with a similar passion to Blair. They place the same faith in the increasingly romanticised voluntary sector, probably without offering the necessary funding, and like their hero will place the alliance with the US at the centre of foreign policy. Unlike with Blair, the alliance will be deepened by hostility to the EU.

But here is the twist: late Blairism was not popular. The more he moved into his own comfort zone, with the keen backing of Rupert Murdoch and Conservative-supporting columnists, he and Labour slumped in the polls. This was not because he was taking the tough decisions but the easy ones, standing "shoulder to shoulder" with President Bush, declaring the end of the permissive 1960s and the rest of it. Polls suggested at the time that voters wanted a change from all of these echoes from the 1980s. Now they get another dosage from leaders who claim, as if by magic, to also offer change.

The choreography of Labour's crisis is utterly gripping and yet is the easiest bit for the political players to handle. David Miliband lets it be known that this time he is ready to stand if a vacancy arises. The ultra-Blairites opt for public silence as a calculated political act. Other Cabinet ministers are publicly loyal, while in private they agonise and scheme vaguely. This is an absorbing drama. Yet largely absent from the script, with notable exceptions such as Jon Cruddas, writing below, is a coherent agenda for change from the still overcrowded terrain marked "Blair".

For sensible ideological and tactical reasons, Cameron will not be the change. He will follow Blair, who paid homage to Thatcher. Ironically, Brown could have been the change. During Labour's second term, he delivered a brilliant lecture on the limits of markets in delivering public services but he rarely refers to those words now. Brown also has a clear sense of political purpose in ways which mark a step forward, with his attempts to turn the challenges of the global market into an opportunity for individuals to fulfil their potential. Partly because of his much discussed strategic mistakes, a caution that makes actual change more difficult, a large dollop of misfortune and the media turning away, he has lost his audience.

Yet with the credit crisis caused by too little regulation rather than too much, a newly fashionable interest in inequality arising from the abolition of the 10p tax rate, the challenges of global warming, the improved but still mediocre public services, there is space out there for a post-Blair agenda-maker, a genuine agent of change who could make Cameron seem like the champion of an outdated status quo. The shaping of that agenda matters more than the political theatre that will be played out over the next few months. In itself, a change in leadership for Labour will not mark a break with the recent past. Changes are more complicated than that.

s.richards@independent.co.uk